the way i am playing, and its going easy:) is to use only crossbowmen (in levels where no monsters are strong against phys) dont upgrade but just spam crossbowmen.
ranged skill of the hero is now 14. basic dam about 35.
some little hints...
make sure you get the money upgrade, then yust let the waves come dont summon them. This way you get more money..
If you want points you need the doll (also with upgrade easier to get, ---> get the accesoires upgrade)
and yust with any TD game look where the mushrooms can hit most when placed
to get hobbits: read instructions and view credits, dwarf:play yhe game 3 times, bombermans: loose 3 times,angel:get all races maxed out in upgrades,red dragon:kill "the end" boss, devil: kill the very last boss
nice game but the upgrade system needs some work... it just clicking the same building twice (i hate that) just played it for a while gonna give it for now a 3 star rank