Get signed up as an iOS dev and for a Steam Greenlight, that’s $100 each. Register an LLC for your company, that varies by state but is at least $300 normally. That’s at least $500.
For the software, you don’t say what you have all ready, and you also don’t say if your a programmer or artist. Licenses for all the Art Software is expensive.
If you register a LLC it’s pretty easy to get into the Microsoft BizSpark program which will give you a couple licenses for all the office software and Visual Studio for for a couple years.