Thread:Pickje07/@comment-22439-20130727085649/@comment-10751008-20130727225303

Getting monsters to level 15 will take a lot of much needed money from you. I think the best idea in your situation would be to upgrade available castles immediately to allow more monsters on that island (more income) so that it'll be easier to purchase your following islands and their castle upgrades.

So basically, finish one island then move on to the next. Save Gold for last.