Hey,
Usually I would suggest having 30+ buy ins for a game type as a bankroll as variance can kick in an leave you broke. However at te lowest levels the standard is usually really bad meaning that you can get away with starting with a little less. In sure 25buy ins is a fine bankroll to start with for nl2.
Have you thought about playing hu sngs? You would g
Have almost 50bis at the lowest levels and the competition is really soft and you very rarely find competent regulars and instead of a 6max table where you have to share the fish you get then all to yourself.
Playing hu you are involved in every single pot and this also means that you can work on an improve your basic fundamentals such as positional awareness, bet sizing, understanding game flow and reading board textures.
Either way whatever game type you choose in sure you can be successful. Ditch Harrington and slabsky and start from scratch with our education services which include hand evaluations, videos and articles.
Good luck
Patrick