First of all, I would recommend that you choose the type of game you like more or feel more comfortable since they are different modalities and in fact the way of playing them differs a little.
Personally, I like to play MTT and, in its absence, SnG. If you opt for this type of games, my recommendation would be that you start playing freerolls or if you have some banking read a good article on banking management (there are many) to avoid losing everything in the first experience.
The game in MTT and SnG is very dynamic and has many different situations, which involve changes in strategy within the same tournament. There are many online articles that explain general strategies to face each phase of a tournament, and it would be enough to start playing in micro limits.
regards