This is a discussion on cash game or tournament within the online poker forums, in the Learning Poker section; to start a bank they recommend playing cash games or tournaments. My box is still small and I can't find the best way to make
I personally started with cash games, and I think, they are the best way to learn the fundamentals of the game. The reason is, they are deeper stacked, in online poker typically 100BB, and for that reason you get to experience a decent amount of turn and river play, which develop your postflop skills. It can be painfull to get coolered for a full 100BB stack in a cash game, but its part of the learning experience. Cash games also offer great flexibility, and they are simple in the sense, that you dont need to worry about things like payjumps or ICM.
There is also something to be said for starting with SnGs and especially the traditional 9 man format. In these you never play deeper than 75BB, and quickly the stack size is reduced to 30-40BB or less, which limit the amount of tricky postflop situations. The concept of outlasting other players can also be more fun to some than just winning individual hands. On the downside ICM is fairly important in a 9-man, so ranges are not as static, as they are in cash games, which can take some time to fully learn. You also need to learn to play shorthanded and heads-up, which makes a 9-man more complex than cash games.
As for MTTs I think, they are generally to complex and require to much time commitment to be suitable for beginners. They should more be your end goal, after you build up a track record in ideally both cash games and SnGs. If you play on PokerStars, the 45 man SnGs are a good replacement for 9 man SnGs, and they are already somewhat closer to an MTT.