When I first started playing online poker I would only run micro sit and gos. I found they helped my learning curve more than throwing $ at cash games. You are able to manage the game flow without having to loose too much. You can also take time to see where you went wrong if you placed outside of the bubble and plan to be better for the next SnG.
Just start out with freerolls. These are great opportunitys to learn and possibly get lucky. I also agree with others when they say to grab some books and actually learn the science behind the game. This will only help you and your bankroll in the future. 2 of the most important keys you should focus on are: Posistion and starting hands. These to me are the most important aspects of the game.