10 buyins or 10% of your bankroll is pretty loose; standard minimum is more like 20 - 30, ie. $200 for $10 buyin at a 0.05/0.10 table. And there are people who prefer more.
And this is regardless of how many tables you play at one time. You may want to have more if you play more than one table at a time, but that doesn't mean you should use less if you play one.
That being said, the lower the level you play, the easier it is to not lose, if you're patient, and the easier it is to back the bankroll with a willingness to redeposit. I started with $50 playing the $10 tables, but that was knowing that I was willing to redeposit, and I wanted an achievable $50 first deposit bonus (ie. if I had deposited $100 I would have to earn a $100 bonus and was ineligible for a $50 bonus; PS didn't pay out in increments of bonus earned)