Always play within you bankroll. For NL ring you need around 15 buyins for each level. So you need to wait until you have $750 to play .25/.50.
My advice is play .10/.20 NL ring still and throw in a few $5 SnGs.
This post will help you understand the concept of BR management: http://www.flopturnriver.com/phpBB2/...pic.php?t=4971
Good luck!