Beanie has a good article on this:
http://bluff.com/news/poker-bankroll-requirements
Starting out here with short bankroll it hard to say, I think playing when your sharp and feeling good is very important. I like to be conservitive with my bankroll, and if you add multitables into the mix I like to add a few more buyins .
Well basically its said that for NL you should have min 30 buyins for FR tables for short handed 6 max 50 Buyins, however I think if your not reckless and have a good grasp of poker knowledge you can get away with less on the micro limits. As long as your willing to move down limits to protect your BR when the poker gods aren't with you then you will do fine regardless of your management.
For me I doing a little shorthanded experiment, on UB instead of multitabling 10 -12 tables I'm trying 2 tables with a bigger buyin. So the amount of money at risk is less than playing more tables yet the chance to win more when I get a decent hand.
Goodluck to whatever you decide.