What boss gives you the most coins and exp?

It depends on where you are at in the game, I also find the more I beat the bosses the less money I receive. However with that out of the way. I am currently a level 80 wolf my family is all 70 and above and every family members elixir stats are at lvl 100. I currently go in a rotation of Furious Bull (Farm), Giant elephant (Savanna), Rhino demolished (Savanna), Old wolf (Valley of Giants), Horrifying lion (Valley of Giants), and Ravenous Crocodile (Savanna lakes). One rotation of this normally leaves me with about 70,000 coins. For anyone lower level I would recommend Ancient Noose (Wild Plains), Giant Bear (Winter Forest), and Mad Sheep (Valley of Giants). I hope this was helpful!

The lion boss in valley of giants

Valley of Giants

Hope this helps you!