Emulators for low end android phone

You an also try PPSPP if the game will run smoothly on you phone. Note that you to check the compatibility list before downloading games on your phone. Most games on PSP consist of  large gigabyte sizes so you can only download few on your device. You only need to play one game at a time anyway. If you keep switching games it will be less enjoyable. Note that most 3D PSP games will run very slow on a low end phone so you only have to pick like 2D games or old ports in PSP. These really limits your games to choose from. There are PPSPP settings you can tweak but it will not be much help. 

MyBoy a gameboy advance emulator for android phone will run smoothly for sure. If retro games are okay for you then this is the emulator to choose. All GBA games I downloaded worked on MyBoy so you never have to worry game crashes, slow downs, incompatibilities, and start up errors. If you want you can bundle download all GBA roms on your phone in torrent sites but this is not needed as you'll need a few decent games.  I suggest having a phone with big screen to avoid eye fatique as text can be too small to read in RPG games, and for your hands as well to properly navigate the touch screen buttons. 

Drastic is a Nintendo DS emulator. This is also a perfect emulator because Android phone is also touchscreen. The screen is gonna have to compensate for the on screen buttons. Like GBA games, almost all DS games will work on your phone even if its 3D. My experience of games here is that they are intended for kids and there are less mature titles, but you're still gonna find a lot fo good games. Note that you're gonna need a stand if you're using a tablet for playing games as tablet can be heavy for your arms to carry.