Okay once you get to London City you have the chance to make loads of money really quickly. Go the the Casino and save outside, next go in and buy 1000 chips, next go to the Roulette table and place 1000 chips on either red or black, if you win then exit the casino and save if you lose exit the casino and re-load. Simply keep repeating this process to gain loads of chips which you can use to buy the skills, golems and items only available at the casino. And you can keep buying items and selling them at the shop to make normal money which you can use to buy the skills and golems in the shop.

Hope this helps