What is the minimum RAM required for Pokemon GO?

Google play store recommends 2GB of ram or more but fewer should still be able to run it but could lag as you've noticed. However another reason for the lag could simply due to a poor connection since the game definitely runs better over wifi.

Source

While Android 4.4 OS system's minimal RAM can be only 512mb, it would definitely not run Pokemon GO smoothly, if it would run in the first place.

In your case, I don't think Random Access Memory is the problem here. Your processor would more likely cause some lag.

Most Android devices have 2GB of RAM and that seems to do just fine amongst many players.