Witch android mobile should I buy?

[GuilhermeGS2]

Sorry, but you won't find a cheap phone for Dolphin (here in Brazil, at least). You'll need a 64bits processor with high clock (high single-core performance, it's essential for emulation), so don't look for higher core quantity, a nice GPU also would be fine, but avoid Adreno, it has poor OpenGL drivers. The popular phones today are based on old Cortex A7 with two quad-cores processors, the Cortex A7-based CPU's haven't a great single-core performance, but still decent for most apps. Also avoid Mediatek, they are too weak, even for PPSSPP.