Going by the 10-interval general rule for worlds (of course this is generalized and typical does not work perfectly), wizard city 1-10, krokotopia 10-20, marleybone 20-30, mooshu 30-40, dragonspyre 40-50, celestia 50-60, and so on... I would say around level 25 would be good. If you find you are struggling, I'd say around level 30 would be ideal :)
lv.23
lv.36
