It really depends on the game, the only game I really play is long range rifle, and it's a gear whore's wet dream, but damn it gets spendy. Some of the least expensive items can give you huge strides. BUT there's certain items you just can't skimp on and none of those are cheap.

Best thing I can say for a guide, is see if you can test drive someone else's wiz-bang gear and if it works better for you, then it's an advantage you might consider, If you don't instantly feel it as an added benefit, it's probably not worth it. You'll know immediately.