Depends on your budget.
Always go with the most up to date version of windows, so in this case, Windows 10
For a processor, I'd go with an intel i5 or an AMD FX-8350 (the amd is going to perform a lot better and is less expensive than intel)
For RAM, you really don't need anything more than 8GB, but if you want, you could get up to 12GB or 16GB depending on your budget.
Hard drive space, get at least 1TB.
For a graphics card, I would go with a GTX 960, but depending on your budget, I'd honestly rather see you get a GTX 970 4GB because it will perform a lot better and will last you a lot longer compared to the 960.
If you got any budget details you could throw at me, I'd be glad to help you.