ajvilladelrey :
I have my AMD Athlon 64 3500+ 2.2gHz with 2Gb RAM and 300w PSU, It's hard for me to find a gaming graphics card because the case of my motherboard is not for high-ends type graphics card. Kindly help me decide on which mainstream graphic card to buy that can run online games like League of Legends and others at 40 to 60fps stable. Thanks in advance...
You are better off investing in a new computer than trying to cram a new graphics card in. With your CPU specs, you will not even be able to run LoL smoothly even at very low settings. Minimum requirement for LoL is 2.0+ ghz CPU and 2 gb of ram. Since LoL is a very CPU dependant game and not GPU, your computer will just struggle to even load the matches and lag through the gameplay even on low settings. You'll most likely get 30-35 fps max on your computer even with a HD 6770 and in ARAM matches it makes it much worse. ---> ARAM in LoL drops your fps between 8-15. So effectively you will only get a max of 25-30 fps with your machine. Not ideal for playing fast paced skill shot games when you lag.
Because your CPU is a single core running at 2.2 ghz, most of the online games today require a minimum of at least a dual core for performance wise (not graphic). Also having a newer GPU will not give you stable FPS because your CPU will just bottleneck the GPU.
So there is absolutely not point in investing money into a newer GPU when you CPU will just kill it and drag the performance way down. You're better saving some money and investing into a brand new computer.
Hint: AMD rebranded their laptop quadcore and dual core chips into desktop line for extremely cheap and low power efficiency. You're better off investing in one of those than keep that ancient machine of yours.
As a comparison for you, my old laptop has an AMD Turion 2.0 ghz dual core with Nvidia 8400M graphics. And even that laptop can only get fps of 45 at medium settings without lagging and dropping to ~38 on ARAM.