I just started back up again after years away from
online poker. Right now I am grinding a lot of freerolls. My advice to you if you play them is to fold early till most players at your table get that shoving business out of their systems then play tight aggressive with some flexibility in your playing style based upon the situation.
Freerolls are brutal. I have been called with a huge pocket pair preflop all in with nothing more than some 83o or other such business and got busted when two pair or trips land for the villain. You will get tilted and you will wonder if the game is rigged from time to time. LOL But persistence, discipline and more patience than GOD himself, go along way in making a deep run in freerolls. Plus it's a great way to learn the game and improve your skills while trying to make money but spending no money.
Look at it this way, if, with your starting $10, you lost it in 3 hours, you lose nothing on freerolls in the same three hours but have an unlimited amount of tries to improve your game and win $.
Aside from just playing them as much as you can stand, I also suggest studying, reading as much as you can about strategy, math, player psychology and anything else about poker you can get your
hands on. I also like to watch the poker guys on Twitch play their MTT's. A lot of them have some useful commentary especially where math is concerned. Some of them will tell you why they call or fold in certain situations and some will even go over hand analysis their viewers submit to them. It's entertaining and informative at the same time.
Good Luck on your Poker Journey!