Get to level 10 on the priest the normal way, then take him to Deadmines, park him within range of XP (move him now n then) and just run through on the lock dotting everything, or gather with the VW/Felguard then use SoC.

Once he's 15 you can access the next dungeon and so on all the way up to
50+ (do SM from 20-35ish then ZF or stay in SM Cath til 40+)

Get to 58 then hit outland