I play this game way too much and see way too many people have way too many bad ideas. I hope this can help some of you learn and win more.

Heroes:
There is no requirement for your draft but there are a few incredibly strong heroes. A dedicated tank however is strongly recommended. Dragon Knight, Undying played as a tank. Enigma, Lich, and Witch Doctor played as damage casters. Shadow Shaman, Lion and IO played as support casters. This is not a list of the only viable characters, just some of the easiest to execute while also being powerful.

Items:
This is going to be the most long winded subject because there are many insanely good items you need at different stages and I need to justify all of them.

BottleRunes spawn every 2 minutes. You can store a regen rune and become a tank or tank even harder. There's no excuse to not buying Bottle because you can even sell it later and easily make your money back. Or don't sell it and back pack it because Regen Runes are B O N K E R S and there is no backpack cooldown.

Urn of Shadows/Spirit Vessel Is the most gold to impact value item in the shop. It provides helpful stat bonuses with bonus armor and mana regen. The active ability heals for more than a Healing Salve. You will definitely get your money back by using Vessel instead of spamming healing salves. The price is cheaper by 2000 compared to Health Bag Level 2 which brings me to

Health Bag Level 2. Its an upgraded version of Spirit Vessel with different stats and a weird healing calculation so I'll just give you some numbers to give you an idea of when to buy it/who to use it on. 2000 max HP = 100 HP/sec. 3000 max HP = 114 HP/sec. 4000 max HP = 128. Personally I think Spirit Vessel is better because the cooldown is a little lower and costs WAY less gold so you can buy something else. If you're a dedicated Healer HP bag is the way to go, if the team doesn't have a healer and you need to fill another role Spirit Vessel will be your best friend.

Platemail (and its upgrades) Armor is incredibly important in this game especially for tanks. Most enemies hit for 400+ damage which will shred through anyone not building Platemail and its child items. This does not exclude Dragon Knight. Use your own judgement when deciding which upgrade you need. If you're on the back line you won't need this.

Pipe of Insight The earlier you get it, the better. Many bosses have one way or another of dealing magic damage and a few of them even wield Magic Blade causing them to deal magic damage per attack. These Magic Blade bosses bosses are incredibly lethal to teams without magic resistance even with a hard tank (who should be building magic resist). Warrior's Emblem does not substitute Pipe because you will lose stacks incredibly fast to all bosses and gives LESS magic resist for MORE money. If you have cooldown reduction consider purchasing a Glimmer Cape (which also happens to be very cheap) and spamming it on your tank to give them +60% magic resist.

Vladimir's Offering/Vladmir's Offering Level 2 +4(6) Armor, +1.5(4) Mana Regen and +Lifesteal for your whole team makes Vladimir's Offering one of the most gold to impact value items you can buy. Every team should have one even if you're a bunch of casters. Even if you don't benefit from the Lifesteal which is the main selling point, the armor and mana regen easily help the item pay for itself.

There are plenty of other great items but but these are just some of the most helpful you can add to any build. I may add more advice/builds later but at this point I'd rather go back to enjoying my Saturday night :)