40 and 300........40 BB at the table you want to play at and move up to next level when you have 300 BB's at the next level increase in your bankroll.
I play micro Hold Em. The rule of thumb I use (read it somewhere) is 40 BB at the table you want to play in. For me I started with $ 6.00 and played at the .01.-02 tables until I reached $ 12.00 or 300 BB's of the next level which was .02-.04.
I also play in the NLH freerolls
and sometimes when I get lucky and win, it helps contribute to get me to the next level.
Hope this hepled...I am sure there is many more opinions out there.