Iceborne Armor Progression (until Velkhana)?

[Tyrsky]

Using Poison GS (Datura Hellspine I) and Beo+ Full Set (inc. Venom Charm II). My goal is to farm up Velkhana's gear whenever it's available. My question is, should I farm some other set during Iceborne or just struggle a bit and try farm Velkhana with this setup?

If it's even possible that is. I accidentally encountered Velkhana during an expedition and it didn't seem that tough (didn't kill it obviously). What item sets/weapon should I farm if needed?

Options:
Rath Heart+ (manageable, I think, that Rathian Surspike though..)
Barioth+ (farming would take quite a while, as I have more resources for Rath Heart+ set)

My current progression is MR 11 (or 10), would mention the exact quest but not sure if it's still a spoiler, but apparently there's still some ways to go until Velkhana becomes available for farming.

[FrozenFruit]

Nargacuga set. The True Razor Sharp is useful on fast-hitting weapons which eat through their sharpness, but I don't think you need it on GS.

If you want more Poison, there are Rathian set, pink Rathian set and Artian set.
If you need Guard Up, there is a Uragaan set.
If you want more critical rate, there are Glavenus set and Acid Glavenus set for Maximum Might Secret. Or there is Agitator Secret from Brachydios set

Also, keep in mind that 1st part of the Velkhana set bonus does not apply to Poison damage.

[CookedMeat]

Build doesn't matter much during progression, especially when you're playing a rather straightfoward weapon like GS.
First you need Health Boost 3 for the best QoL (Prevent one-shots)
Then you can get some evade window or evade distance to keep you staying alive better.
Then maybe some focus or quick sheath as they work well with GS. (Draw charged attack, sheath, roll away and wait for next attack chance).

Most offensive skills are rarely seen in progression armor. If you want a decent offensive quest, for example and affinity based set with stuff like Critical Eye + Critical Boost + Weakness Exploit, then you will need to sacrifice a lot of QoL skills.

Since you're here asking for builds, I presume you are not very experienced with the game yet, so each fights might take 15-30 minutes. If so, try focus on preventing deaths, then improve on evading attacks. By taking less hit means you will spend less time recovering, thus more time to attack. Such improvement will bring you more benefits (in terms of shortening hunt) more than any offensive builds you could get at your point in the game.

PS. Poison only deals very minor damage to the monster, and should be considered as a bonus rather than your main focus on building/selecting a weapon. For GS (and generally most melee weapons), you should focus on weapons with high raw attack, high affinity, and good sharpness.

[Tyrsky]

Poison as an element kind of just happened, it was an easy-to-get element in the early game so I kind of got stuck with it and only played as a poison based "build". Then in Iceborne I started to look at builds more closely and there was a GS Progression Guide on Youtube which I've been following and apparently it's also suggesting using Poison as an element so I continued with the same build.

Beo+ set was a starter set suggestion for MR in that guide and there were some mentions how to upgrade it, but the guide didn't actually mention when a upgrade was necessary. I probably should upgrade by just the feeling I get from fighting monsters but it's difficult to gauge when it's your first playthrough through the game. But absolutely, fights take rather long, usually 30+ minutes each which even to me sounds like a lot.

I upgraded to 2 pc Rath Heart and Datura Hellspine II for now, considering upgrading to fully to Tigrex Set (excluding weapon) until Velkhana if necessary. I had Critical Eye and other useful skills through Decorations with the Beo+ Beta set, but I was stupid enough to upgrade to Rath Heart+ Alpha and can't equip the Decorations anymore, apparently.

[CookedMeat]

That's the tricky part when trying to build for yourself in MHW.
Optimumly, you want armor with good skills and slots, so you have the most freedom to tweak the build to your favor. During progression, most armor pieces have little slots and crappy default skills, which is why you often have to sacrifice a whole lot of survivability to trade for offensiveness.

I believe the video guide you mentioned recommended poison GS not mainly because of its poison element, but rather the GS have good stats and just so happen to be a poison GS.

Most offensive skills in MHW only increases your theoretical damage by a few %. However, if you learn to aim for monsters' weak spot then your damage might increase much more than that. For example Rathalos head takes about 2.2 times more damage than its leg. So, I recommend getting enough defensive skills first to keep you survive well during a fight, then some QoL skills like evade window to give you enough mobility to focus on attacking a monster's weakness without putting yourself at risk.