As others have said, its fine to try everything and play, what you enjoy. However if you are serious about online poker, I really dont think, you should start out playing MTTs as your main game. They are in a sense the most advanced form of poker, and they require a wide variety of skills. They typically start with 100-200BB stacks, but quickly you move into playing with a <50BB stack, so to learn 100+ BB poker in MTTs you have to play a really large number of them, and you are only practicing this skill like 10% of the time.
On the other side they also require understanding of shorthanded final table play, and since its difficult to reach the final table in a large field, again you are only practicing this a very small percentage of the time. Finally there dont run many MTTs, that are friendly to a typical beginners
bankroll. Sure there are some 1$ or even 50c buyins, but you are not going to get any sort of volume playing only these.
So while its obviously fine to chill out on a Saturday or Sunday and play an MTT, even one that is technically outside your bankroll, the main game for a beginner should either be 2-5NL cash or 25c-1$ SnGs. Stars is a brilliant site for both of these game formats, because the rake for 2-5NL cash is low, and they have a lot of multi-table SnGs at these lower limits, that tend to run all the time. So rather than wait hours for the rare time scheduled 1,1$ MTT to start up, just buy in to a bunch of 45 man SnGs and grind away.