I’ve been playing for several months and I’ve noticed that lately the game has been disproportionate to start training heroes, we spent days to come 2 *. Totally unfair and unmotivating spend hours in the game waiting to improve the team and receive one of those. I really liked the structure, the graphics but the strategy released for some has no way to go to play unfortunately. You have seen a month and see if I am wrong, after I will uninstall because I am waiting and I can not evolve.
Have you read Coppersky’s Compendium (a game guide written initially for new players)?
I highly recommend it:
http://tinyurl.com/CopperskyCompendium
Also, are you aware that you can make your own 2* heroes (see Training Camp), and even guaranteed 3* heroes by Training Camp level 12?
There are many options in game, some are more apparent than others. 
Good luck!