Note that you cannot overclock anyway with your unlocked i7-7700K on a B250-chipset motherboard, so, air-cooling is a logical choice. The type of air cooler will also depend on your case's airflow capabilities/space clearances. Check the specs of your case against the height of the CPU cooler if it will fit.
I recommend getting the Cryorig M9i, an affordable CPU cooler, low-noise, small-tower type/not bulky, and good heat-dissipation. It only costs ~$35:PCPartPicker part list
/ Price breakdown by merchantCPU Cooler: CRYORIG - M9i 48.4 CFM CPU Cooler
($34.88 @ OutletPC) Total:
$34.88Prices include shipping, taxes, and discounts when availableGenerated by PCPartPicker 2017-06-09 12:03 EDT-0400