I like Barty1884's build. But you can save a little money and run windows without buying it right away. I am not saying to not buy it, but you can build the rig and run windows unactivated till you get the cash to have it activated. With that $100 saved you can get a SSD and a RX580 that comes with a couple of decent games.
This is not a budget system, this is a solid midrange rig.
PCPartPicker part list:
https://pcpartpicker.com/list/wdxCvn
Price breakdown by merchant: https://pcpartpicker.com/list/wdxCvn/by_merchant/
CPU: AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor ($159.99 @ Amazon)
Motherboard: Gigabyte - B450M DS3H Micro ATX AM4 Motherboard ($54.99 @ Newegg)
Memory: Team - Vulcan 8 GB (2 x 4 GB) DDR4-3000 Memory ($69.99 @ Newegg Business)
Storage: Samsung - 860 Evo 500 GB 2.5" Solid State Drive ($72.99 @ Amazon)
Video Card: PowerColor - Radeon RX 580 8 GB Video Card ($189.99 @ Newegg)
Case: Corsair - SPEC-03 Red ATX Mid Tower Case ($33.98 @ Newegg)
Power Supply: Corsair - CXM 550 W 80+ Bronze Certified Semi-Modular ATX Power Supply ($29.99 @ Newegg)
Monitor: Asus - VN248H-P 23.8" 1920x1080 Monitor ($89.99 @ Newegg)
Total: $701.91
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-11-27 12:46 EST-0500