well... you cannot upgrade to another CPU without having a motherboard that supports it's socket type. In this case it's teh LGA1151. You current socket is AM (varient), which will not work with the LGA1151 >>> this means >>> CPU upgrade comes with Motherboard Upgrade >>> Motherboard comes with newer Ram upgrade.
but you mention 7700k, likely cuz it's getting real cheap. well that's because the 8th gen intel CPU i5 is on par in performance with the i7 of the 7th gen, and it's cheaper!
Here would be your mid range upgrade:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel - Core i5-8600K 3.6GHz 6-Core Processor ($279.89 @ B&H)
CPU Cooler: Cooler Master - Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($24.39 @ OutletPC)
Motherboard: ASRock - Z370 Extreme4 ATX LGA1151 Motherboard ($156.98 @ Newegg)
Memory: PNY - Anarchy 16GB (2 x 8GB) DDR4-2133 Memory ($134.99 @ Best Buy)
Operating System: Microsoft - Windows 10 Home OEM 64-bit ($88.89 @ OutletPC)
Total: $685.14
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-11-19 21:48 EST-0500
I included win10 becuase im sure you'll need it, this upgrade could come much cheaper, if you wish to sacrifice:
This is a non-overclockable upgrade, which is still very capable of gaming very well
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel - Core i5-8400 2.8GHz 6-Core Processor ($199.89 @ B&H)
Motherboard: ASRock - Z370M Pro4 Micro ATX LGA1151 Motherboard ($121.98 @ Newegg)
Memory: Team - Elite Plus 16GB (2 x 8GB) DDR4-2400 Memory ($129.99 @ Newegg)
Operating System: Microsoft - Windows 10 Home OEM 64-bit ($88.89 @ OutletPC)
Total: $540.75
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-11-19 21:50 EST-0500
again, windows 10 included
If you plan to keep your GTX1050 then even a 400-450W psu will suffice. But generally for having a better GPU in mind later on, you should aim to get a good quality 550 ~ 650 W psu