Nice game in principle, but has two fatal flaws:
1) It's a money grab and constantly bombards you with you with special "bargains". It gets extremely anoying.
2) The timing of guild expeditions works in way that will neither allow continuous activity (as f2p) nor lets you run aa expedition longer than 1 hour. As this is an important part of the game involving multiplayer, it encourages an unhealthy playing style.
I really like the game otherwise, but will probably stop playing for these reasons.
Many levels require strong cards. So you need many cards for fusion. But you can´t actually get more than one per day, without paying real money for it. It would be usefull, if replaying a level would give cloverleaves.