honestly id have to say fighting is quickest, my digger trakes years but makes cash quickly lol. fighting you at least get xp in large amounts whereas with other skills you get much smaller, constant amounts. overal if worked out thouigh id say fighting was sill much quicker.

set your rank to tough or around that and just keep clicking and healing. get a miracle satchel or 2 and a few prayer wheels so you dont have to keep making trips back to the CC and just go a'clicking!

and for all of those diggers looking for work...
building is a solution as well... :p

Trouble

Just DO kings'S missons. It gives really more exp.