YouTube fast, gaming sucks

[YukonTrooper]

Do you have another NIC to test with? You may as well try nailing down the problem before throwing cash around.

[Chareon]

Another possibility is to try moving your computer back closer to the router, just briefly to test if your performance improves with being closer.

Personally though I'd just drop wireless as it is so unreliable in general due to the nature of the technology and go for powerline as others have mentioned.