For a level to be considered "complete", you must collect all big chests, little chests, and secret items (in the form of pink bows, wanted posters, plate of waffles, etc). The Ogre Camp's secret items are obtained through the act of bartering. Not by finding them. So to complete that specific level, you must buy all upgrades from the store. Most of them are obvious and out in the open, thus creating a complete collectible walkthrough would be mostly pointless and cause people to take longer reading it than needed. If you're really struggling, feel free to check around the Sherk: Forever After forums, found Here.
You should only worry about getting the 100% on each level after you have completed the game so that you have obtained all special abilities for every character.