You will need to buy every item in the store at the Ogre Camp. To get everything available to purchase there, you must complete the campaign. To have enough coins to purchase them all, you should have done almost all 100%s on every level. There are a total of 11 different categories to buy from, most having three different upgrades. If you want to speed this up, purchase the "Money Up" upgrades first. You will need roughly 15,000 coins to be able to purchase everything.
Check out this picture if you need some help.