With Dark Souls III looming in the horizon and recent releases of high-end games lately, I have constantly been hitting a certain problem

My computer have become obsolete for gaming

Instead of buying complete computer this time around, I decided to dip my hand at the magic of building your own PC but i'm completely clueless about the inner workings of computers, so I need a lot of help!

The computer will be mainly focused on gaming, however it doesn't have to run every single game in max graphics, as long as the games run well.

Notable things:

Budget : around 500$-700$ (it can go slightly over if must)
Peripherals : only thing I really need is a suitable monitor (doesn't have to be included in the initial budget, but would be preferred)
USB slots! : i'm sucker at buying items with USB connectors, so I need multiple USB slots in the tower
Longevity : while I know that individual components can be upgraded periodically, I rather not do it once in every month
Shipping : site where I can order all of the parts all the way to the finland

If you guys have any further questions you would like to know, ask away and I try to answer as well as I can.