At a NL table you want to buy in for the max allowed so that you can maximize profits with big hands. At a limit table you just want to always make sure that you can cap every street if you need to in case you do get a monster.

The bankroll requirements are 300 BigBets for Limit; and at least 15 buyins for NL. If I were you I'd be more tempted to put $150 in and then you would be bankrolled to play either .25/.50 Limit or $10 NL (max buy-in = $10).