i lol'd as well.
-Why should you get to level 30 to have fun? I'm 10 only atm and I'm having a blast.
-You can either purchase them instantly with RP or unlock them with IP, and some are very very cheap and others have special discounts from time to time. if you're dead set on getting someone you can always save the IP you gather and you'll get him eventually. Not to mention each week there is a set of free characters available, and usually by the time you try them the week ended
-Why bother? Just to have an extremely slight advantage? Sure you can, you're not forced, the loss ain't big. It's not like wow, if you miss something you dont lose much. But if you insist on getting those there's always the option to spend RP and get them instantly.
(LoL is free, RP=Riot Points(pay money to get them), IP=Influence points(get them steadily after each battle).)