The Oracle is a starter GB. Don’t waste too many fp on it as you will soon be deleting it. You are better off getting a Zeus and leveling it up. But to answer your question put your fp into tech till you get to the end of the tech tree for your age. That will give you access to the best buildings and troops of the age you are in. It’s best to try to play a balanced game. You want to make enough coins, supplies, and goods to get by and to be able to use your fp to progress in the tech tree and to level up the GBs that you get.