Is this a nice budget build?

What do you plan on using it for?

For gaming, you should consider dropping to a i5-7400 and put the money into an RX480.

Also, you can't overclock with the B250. The only reason to get a K-series is to overclock, so either switch CPUs or get a board with the Z270.
 
Better and cheaper:

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-7600 3.5GHz Quad-Core Processor ($215.99 @ SuperBiiz)
Motherboard: Gigabyte GA-B250M-DS3H Micro ATX LGA1151 Motherboard ($69.99 @ Amazon)
Memory: G.Skill NT Series 8GB (2 x 4GB) DDR4-2400 Memory ($57.99 @ Newegg)
Storage: Sandisk SSD PLUS 240GB 2.5" Solid State Drive ($74.99 @ Jet)
Video Card: Zotac GeForce GTX 1060 6GB 6GB Mini Video Card ($219.99 @ Amazon)
Case: Corsair SPEC-03 White ATX Mid Tower Case ($56.99 @ Newegg)
Power Supply: Corsair CXM 450W 80+ Bronze Certified Semi-Modular ATX Power Supply ($49.99 @ NCIX US)
Optical Drive: Lite-On iHAS124-14 DVD/CD Writer ($16.89 @ OutletPC)
Wireless Network Adapter: TP-Link TL-WDN4800 PCI-Express x1 802.11a/b/g/n Wi-Fi Adapter ($34.98 @ Amazon)
Total: $797.80
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-04-17 15:42 EDT-0400