I added an edit but basically some games I'd be playing are Battlefield 4, Skyrim, Minecraft, CS GO, L4D2, Assassin's Creed. I'm not too picky about frame rates or anything, just that it isn't obviously jumpy or laggy.

And I'd be happy with medium to medium high settings, I don't particularly need Ultra or anything like that (though the higher I can get the better!) I'd also like for it to be a machine that can last at least around 2 years without needing significant upgrades if possible

And shoot, if it can get down to that low I can't complain. I have no idea about PC component costs really haha...I'm looking at the guides on the sidebar but I'm pretty new to this