Here is a nice little game called Pocket Creature.
You build your army to overthrow the King, the faster you are, what means the less level you need, the more points you get.
At the start you have to buy 2 monsters. You can buy a dragon and a puppet, then you have all creatures, because you start with a spirit and an undead. But I myself bought a second undead and did it in 46 days/missions!
the game is very simple yet addictive,
have fun :)