here are few tips,
Finding a good guild: This is absolutely crucial to success, particularly as free to play.
Familiars: These should 100% be a focus.
The sooner the better, because you absolutely should get Aquiris to adult. The extra stamina is invaluable. It allows more medals, more progression, and more ranking. And, it gives you more speed ups. 100% get familiars and get Aquiris to Adult as soon as you can, level him as high as you can iphone trade in.
After Aquiris, if you can, unlock Pact 2 and get Harpy to Adult first. Not only is the VIP points huge, her increased Shelter is incredibly important, even more so for a F2P player.
After Aquiris and Harpy, the next one is up to you. Bonehead, Totempest, Territe, and Tempestite all are good, about equal. Just depends on what you want/need at the moment.
I recommend 2 gyms, because every hero added to training after the less gives less experience than the one prior to it.