Freerolls are a great way to start out in poker. Pokerstars are currently running $100, $200 and $300 tourneys every day. One day it will be $100, the next $200, the next $300, then back to $100 and so on. The structures are a little weird, because the payouts regardless of the prize pool are exactly the same up to 27th. Then they all pay $0.10 up to 800 places, the $200 one then pays $0.10 to 1,800 and the $300 one pays up to 2,800. So the $300 one is much easier to cash in than the $200 one and much, much easier to cash in that the $100 one.
You can essentially limp your way to a cash in the $300 tourneys but this is not going to teach you an awful lot or give you much of a chance getting to the bigger money and the final table. To cash in the $100 ones you've got to play some half decent TAG poker and dodge the lucky donkeys.
Once you've built your bank roll to a couple of $'s I would move on to the multi-table SnG's I like the 45 seaters, but I also play the 90 and 180 games as well. $0.25 buy-ins means your not risking loads of money, but you will start to play against better players that aren't going to look to shove pre-flop every hand.