The sensitivity (dpi) of the mouse is not in any way equivalent to the accuracy of the mouse.
Many gaming companies sell laser mice that have "6400 dpi" sensors, this means that you can move across a 1080p screen more than 6 times by moving it an inch. (6400 dpi means that the mouse moves 6400 dots per inch, and 6400 pixels per inch) This is not needed in a game like counter-strike or any game, and 6400 dpi mice are typically less accurate than 400 dpi mice when they are at the same setting.
Now that I've explained that, here are the things that contribute to the tracking of a mouse:
acceleration (makes your cursor go farther (positive acceleration) or less than the place you wanted to go(negative acceleration) )
prediction/anglesnapping/drift control (feature that forces your mouse to draw in straight lines)
maxperfect control speed (how fast you can move your mouse until it stops tracking perfectly)
malfunction speed (how fast you can move your mouse without it being unable to track)
lift off distance (how far you have to lift up your mouse to stop it from tracking)
the perfect mouse for you, would be the one that is a SHAPE THAT YOU LIKE, has 0 acceleration, no prediction, a high malfunction/perfect control speed, and a lift off distance that you prefer.
An important part of finding a mouse with a shape you like is finding your preferred grip. Many mice are made based around pleasing players who grip their mice a certain way. Play around and see which of these grips you prefer, and try to factor in what your grip is and what grip the mouse you're looking into purchasing was made for.
But how will I find a mouse that fits this criteria? well, it will have to be an optical mouse which is what most competitive CS players use, every single laser mice has acceleration problems, which you cannot learn to aim with because it changes your aim every single time you go over a slightly different surface (ie: microscopic bumps).
Most good optical mice use an AVAGO-3090 or AVAGO-3050 sensor or similar (many mice use these sensors but have bad firmware that ruin the tracking), avoid pixart sensors such as the ones used in all optical steelseries mice/zowie mico, they have predicition and a low perfect control speed.
Great mice that either use the Avago-3090 sensor or are extremely similar are:
Coolermaster Storm Spawn
Deathadder Black Edition
Deathadder 2013 edition
Abyssus (great shape for quake, not so much for counter-strike)
MX518 (has prediction problems)
Roccat Savu (has tracking problems on a lot of surfaces)
The MLT-04 Electronics sensor, which is what is used by a lot of professional gamers in Counter-Strike and Quake is found in the old Microsoft mice:
Microsoft Intellimouse 1.1a (IMO 1.1a)
Microsoft Intellimouse 3.0 (IME 3.0)
Microsoft Wheel Mouse Optical 1.1a (WMO 1.1a)
Microsoft Blue Optical Mouse (discontinued since forever lol)
The MLT-04 sensor is great, and is why its still used by some amazing CS players today, it has no prediction, positive acceleration, etc + it includes a great lift off distance The only problem with these mice is that they get negative acceleration if you pass the max. Perfect Control Speed (which is 1 meter per second at 125hz polling rate, or 1.5 meters per second when overclocked to 500hz or 1000hz, which I will cover how to do later)
If you are looking for a cheap gaming mouse, I recommend the Wheel Mouse Optical 1.1a as it is better than most of every gaming mouse you can find on the market and it costs about $5 on ebay.
I think the most important thing for gaming is the monitor, so I put it just below the mouse in this guide.
When you're gaming, the most important aspects in a monitor should be:
Refresh rate (how many frames per second the monitor displays)
CRT vs LCD
CRT IMO, CRTs are king for gaming, they have absolutely no motion blur because of the way they flicker, and you can use any resolution on them and it won't be blurry. They have 0.05ms to 2ms(phosphor decay) input lag, and they go up to very high refresh rates.
A common misconception about CRTs is that they cause eyestrain, they will only cause eyestrain if you keep them at 60hz. Most CRT monitors will go up to 80hz on their normal resolution (this is enough to reduce the flicker and stop the eyestrain). The reason CRTs cause eyestrain is because they flicker, but the flickering of a CRT also removes any perceivable motion blur.
I use a Sony G520 Crt with 1024x768 @ 160hz, (most CS:GO professionals use 1024x768 @ 144hz), I will link the guide for overclocking your monitor at the bottom, it may work for LCDs but it works much better with a CRT.
As for LCD, there is only 1 decent LCD monitor as of this guide. It has around 5ms lag and some motion blur ASUS VG248QE Black 24" 144Hz 1ms
There are only a few qualities you should be looking for in a mousepad:
Since Counter-Strike is a game you should be using a low sensitivity on (to score headshots or get more accurate crosshair placement) you will probably need a big mousepad.
One of the biggest factors of a mousepad is that the glide degrades after you use it for awhile, the Steelseries QCK+ is used by many professional gamers because when it is worn, it tracks slightly better broken in.
I use a Steelseries QCK Heavy because its durable and has a lot of control for aiming.
Mousepads I recommend:
Artisan mousepads (Made in Japan, "QCK killer")
Razer Goliathus (speed edition = similar to qck, control edition = very slick like hardpads)
If you want a slick surface, I would recommend finding a slick cloth pad, my experience with hardpads is that they degrade your mouse feet quickly.
These are the factors to determine which headphones to buy for gaming:
These headphones are designed by very prestigious headphone companies and audio engineers, they aren't just some cheap speakers and a microphone packed into a gaming package with virtual surround sound and sold to you for a quick buck.
To be honest, I don't think theres any difference between using virtual surround sound with a good pair of headphones like the AD700s and not using virtual surround sound. When you are using audiophile headphones with an open design it creates an authentic surround sound. I could probably hear a dime drop across the map and tell you the exact position.
Personally I use the HD 598s because they're great for music and gaming. If you truly want and need a headset, go for the Sennheiser PC360 because they're the only decent one.
Heres a list from the resource below, copied from a person that has tried tons and tons of headphones including siberias, and probably whatever gaming headset you use.
cherry mx reds>membrane/rubber dome cherry mx black>membrane/rubber dome membrane/rubberdome>cherry mx blue/brown/clear etc cherry mx red/black is by far the best switch for gaming and this is not debateable. they may not be the best for typing
i'll say i recommend the CM Quickfire pro with cherry mx red switches on a budget, and a Filco Majestouch 2 with reds if you want a full size, highest of quality keyboard
Edit: hi I'm not the guy who made this guide but I want to throw in a bit more information about keyboards
helder seems to have totally gimped on keyboard information despite the fact that he obsessed over them for a while
there are only three important things you want in a good keyboard:
High key rollover
Good feel (subjective)
Preferably PS/2 connection (correlating with first point)
generally, membrane and rubber dome keyboards (if you don't know what keyboard you are using, you're probably using one of these) aren't very good for playing games of any kind. they're cheaply made and mass produced, and usually only have 2-4 key rollover
the reason why you want a high key rollover for playing video games is because a lower one will make simultaneous key presses impossible. so, with a 3kr (3-key rollover) you'd be able to click 3 buttons at the same time without your inputs being stopped and no longer registering. many companies advertise a higher key rollover as "anti-ghosting", but it is, in fact, incorrectly named, and at this point is merely a marketing term. usb connection keyboards limit the key rollover to 6kr, which is fine for pretty much all games unless you're playing beatmania or o2jam.if you really want a keyboard with NKR (any number of keys can be pressed at the same time and still register), you'll have to get a keyboard which uses a PS/2 connection. also, PS/2 connections don't poll the way USB keyboards do; instead, they send a signal to the PC when they are told to (when you activate a key) which causes a hardware interrupt, forcing your CPU to register the keystroke. this is superior to USB's polling, because it forces an instant interrupt. also, it can't be delayed by other devices taking up bandwidth on your USB bus, and won't constantly and unnecessarily poll your CPU, which will only waste CPU time. PS/2 wins on every front here.
for a keyboard with a good feel, you'll want to get into the market for a mechanical keyboard. the keyboards helder mentioned earlier in this section are very nice keyboards. i actually use one of the keyboards he recommended, the filco majestouch2 with red switches. the reason why we prefer Cherry MX red switches is because they have a very light required force to activate the keys and are linear. this guide is really great for learning about all the different types of switches: http://www.overclock.net/t/491752/mechanical-keyboard-guide
however, among the most popular switches made by Cherry Corp, which is the most well-recognized brand of mechanical keyboard switches, the key differences are:
Cherry MX Blue:
low required activation force (which means the keys aren't resistant to being pressed)
tactile (which means there is a tactile "bump" when you activate them, allowing you to feel when the switches were activated)
clicky (which means it will make a lot of sound when the keys are activated).
there's one reason why I don't think these switches are good for gaming (my opinion and my opinion only; there are plenty of good players of all games who use these switches in their keyboards), and that's because their release point is far above their activation point, meaning that you have to almost entirely release the key to deactivate it. it makes for an annoying experience, especially for WASD movement, at least in my opinion.
Cherry MX Red:
very low required activation force
linear (which means there is no tactile "bump" when you activate the keys)
not clicky (still louder than your average membrane or rubber dome keyboard if you bottom out the keys, but assuming you type as lightly as possible, you can make these keyboards have next to no noise)
Cherry MX Brown: many consider these to be the in-between of the blue switch and the red switch. they have
low required activation force
they also don't have the problem with the release point that the blues do, which means they probably feel better (although note i have only ever used blue and red switches; my knowledge of other keyboards comes from the internet)
Cherry MX Black: a lot of people consider these a "tougher" version of the red switches. they have
high required activation force (which means the keys have a lot of resistance)
a popular black switch keyboard is the SteelSeries 6gv2, but i've heard mixed things about it. the go-to companies for any of these keyboards are usually companies which specialize in keyboards, e.g. Filco, Rosewill, etc.
AVOID "GAMING" KEYBOARDS WHICH AREN'T MECHANICAL. these keyboards are made of the same material as any other rubber domes/membranes, and are essentially really big scams. Razer sells a mechanical keyboard called the BlackWidow, but i wouldn't recommend buying it because it has relatively low build quality and only 3-key rollover (although it has 6kr in the WASD "cluster" as they call it). it used to be a good budget choice, but with CoolerMaster's recent CM line of mechanical keyboards, it fails at even that (and don't even get me started on the BlackWidow Ultimate; it's basically just $50 extra so your keyboard will light up).
that's pretty much it for keyboards. like helder said, if you're only playing FPS, your keyboard is probably one of your least important tools. however, it's worth it to be educated on what is and isn't a good purchase (since this is a guide about how not to get scammed, after all), and in my opinion, mechanical keyboards (especially red switch ones) are far superior to membrane or rubber dome ones for both typing and playing. there are different types of switches and keyboards out there you could learn about (such as Topre, Alps, and the other switches made by Cherry Corp), and if you're truly interested in learning about them, check out the guide i linked on overclock.net