While I like Stu's idea of having 20-30 SNG buy-ins in your bankroll, I would suggest that you start off at the lowest limits possible, Liza. Even if it means you have 100+ buy-ins in your bankroll. If you're BR is less than 20-30 buy-ins, then BRM doesnt really apply and you're forced to play at the lowest limits.
If you're not familiar with SNGs and how they play, definitely started of at the lowest limit, 9 handed tables. This is a perfect place to start so you can get an idea of how the game plays, the blind structures, and everything. The game plays at exactly the same in the $1 limit and the $20 limit, the quality of play is very different but the same rules apply. So, if you're looking to play to get knowledge and a better understanding of the game, start at the bottom. And then once you're more comfortable you can move up to the limits your BR allows you to play.
There are few types of SNGs, so I would say to give each one a try to see which is more suitable for you.
Normal single table (ST) SNGs are the most basic and a great place to start for beginners and those new to SNGs. Think of it as a final table in a small tournament.
Turbo STSNGs are similar to normal games except blinds increase much faster. If you're not used to making decisions fast or being forced into shove/fold situations quickly, I would stay away from these games for now. But once you get used to them and know how to play, they're just as beatable as normal STSNGs. The big pro to turbos is that they're a lot faster so you can get twice as many games in as you would a normal. The swings are much higher in turbos, though.
Normal Multitable (MT) SNGs are pretty much like multi-table tournaments. Depending on the site there can be 18, 27, 36, 45, 90, 180, or more player SNGs. While its similar to an MTT, the big difference is the set number of players and the set pay structure. I like playing MTSNGs because it gives me some MTT training as well while being easy to beat (less players). The only I would recommend is to make sure that the pay structure is worth your time to play. For example: say that a $1 45 man SNG pays $14 for first and you estimate its going to take about 2 hours to beat. So, you're making about $6.5 an hour. Now say that the 90 man SNG pays $20 for first and you estimate its going to take 4 hours to beat. So, you'd be making only $4.75 an hour. So, while the 90 man pays more for 1st, you're making a bigger hourly rate for the 45. Its easier to beat a 45 man than it is a 90 man because of the less players and you're getting a better hourly rate, so I would be more inclined to play the 45 seat. There is nothing wrong with 90 seat SNGs, but if you're looking to build up your BR, its something to look for.
Turbo MTSNGs is exactly the same thing as above. I like playing the higher number of player games: 180+ players because first is usually a decent pay-out and it being a turbo means it doesnt take as long, so the hourly rate is much greater than it would be for a normal.