For the 7700k, you need a cooler as the processor does not come with one. THe 7700k is also last gen, so the coffee lake is better suited.
What about storage? Do you need a HDD or SSD?
This build should have all that you need:
PCPartPicker part list:
https://pcpartpicker.com/list/cYpLVY
Price breakdown by merchant: https://pcpartpicker.com/list/cYpLVY/by_merchant/
CPU: Intel - Core i7-8700K 3.7GHz 6-Core Processor ($379.00 @ Amazon)
CPU Cooler: CRYORIG - H7 49.0 CFM CPU Cooler ($34.89 @ OutletPC)
Motherboard: MSI - Z370 GAMING PLUS ATX LGA1151 Motherboard ($111.98 @ Newegg)
Storage: Samsung - 850 EVO-Series 250GB 2.5" Solid State Drive ($89.89 @ OutletPC)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($46.69 @ OutletPC)
Case: NZXT - S340 (Black) ATX Mid Tower Case ($49.99 @ Newegg)
Power Supply: Corsair - RMx 650W 80+ Gold Certified Fully-Modular ATX Power Supply ($74.98 @ Newegg)
Total: $787.42
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-01-15 00:09 EST-0500
With a SSD for OS and HDD for mass storage. If you do mind a Watermark, you can download the Windows ISO off the webpage and not activate it, thus saving money on the OS>