Honestly, i think freerolls are a terrible way to learn solid play. At least in the early stages, when it is just a mad dash to collect chips, even with premium hands, you are still going to bust out to some AWFUL hands a large amount of the time if you get all in preflop. Ive seen insane players repeatedly jam over and over with total rags and stack better hands to the point where their statistical advantage is so great, that it doesnt really matter what you have because at some point they will stack you. Its not fun. The blind structures are designed to accomidate the often thousands of players, by being very fast, and giving you very little to start with, meaning its typically a messy shove fest and unless you are lucky, success is very hard to achieve by skill alone. That said, sometimes you get seated with people who actually love the game and you can learn alot, but its rare imho.
Good luck!