@apolymask,
I am a happy customer of minergate and mining BCN at the moment ;)
I don't think mining BTC via GPU is worthy enough! Or LTC also! If you wish to mine via GPU then try something we can mine easily like BCN, XMR!
If you wish to mine BTC you must go to https://www.bitmain.com/ and check products! You can find a lot of miners there. Personally I like Antminer D3 for Dash coin mining!
Cheers~