Can anyone please help? I have an AMD radeon 7770 graphics card and 8 gb of ram.
Which shader mod are you trying to use? If you're using SEUS, chech that the version you're running is compatible with the version of OptiFine that you're using.. And the compatibility of the MC version with the shader/OptiFine version.
I was running on 25FPS with an i3-4130 and a HD7770 GHz Edition, so 30-40 sounds pretty good! I've recently upgraded to an EVGA 750Ti FTW and it's a LOT higher FPS, around 60-70 most of the time. Your GPU may not be able to handle it as well?
Oh, and if you're using an AMD CPU.. MC is only single threaded by default (unless they've patched that with the 1.7.* updates), so you'll struggle a little bit more compared to Intel users. (slightly better single-core performance)