Build me a mobile and tablet game

I am an entrepreneur with electrical and electronic engineering background. I do not have the time to develop (and learn) to program my own games using iOS and Android. I want to hire someone with this expertise. My business is to develop apps for mobile and tablet devices. This business idea is to develop a tower defense game and generate income from in-app purchases and banner/video advertising. I need to have a game platform developed in a generic way such that I can give guidance on the level design, decide on graphics and storyboards and boss, enemy and player units' attributes. I should be able to test the game before it is uploaded/published onto the Apple and Android platforms. Someone with graphic development is a requirement. Details of the game story and specification have been documented to ensure the game developer and I have a mutual understanding of the requirements. The tower defense game will have about 30 levels with a split from the first 10, allowing the end user / gamer to choose a separate path to follow (i.e. going onto another 10 levels, thereby making it a total of 20 levels per full game). I have attached the game concept design document. Please review this document and explain to me how you will deliver my game concept design into a working game within my budget of 500 Euros. I would like to see examples of graphics you have developed for previous mobile device games. The milestones I propose will be managed very strictly.