Graphic Card Guidence Help

Here is the deal, I have a Game I would like to play (Guild Wars 2) and when I played it
it was lagging like hell so I had to reduce the graphics settings to the lowest i could and the lag went away (most of it). I meet all the system requirement like RAM and CPU, but i think it was the graphics card that was letting me down (i am not to sure about graphics cards so thats why i need your help).

My graphics card is: AMD 760G

So can you please tell me how good or how bad it is and is it suitable to play games like Guild Wars 2 (it has really good graphics just search your self on youtube ).
If not, what is a good graphics card that would play Guild Wars 2 and not lag a bit? and how much money would i need to spend on a good graphics card?

Sorry for bombarding you guys with questions, i just have no knowledge in this stuff and if you were wondering about the system specs for Guild Wsrs 2 Here it is (under game FAQ). if you can help me out that would be great and very much appreciated, Thanks!

Thanks for that just a few thing I want to clarify, will I need a new motherboard for that graphics card? And (the stupidest question of all) if I upgrade my whole computer like RAM CPU and so on will that graphics card still be compatible?

Ok first of all how do I find out my PSU and how do I know if I have a PCIE slot? My budget is about $80 at the moment (would there be any good cards for that price? Ie like the one you mentioned)

If you could fill in your system specs, this will help us ascertain a plan of action and adaquit help for your needs.