So you've got around 430$ dollars, not a bad cash. If you can sell your actual PC and get like 80-100 extra dollars, that'd be great; but if not, let's go ahead:
I am personally a Ryzen's processors fanatic, so as starting I'd recommend you to get a Ryzen 3 2200G - Last year, the best price-to-performance CPU was R3 1200, and this year with 2nd Ryzen generation CPUs the thing went better - good performance, less price.
As for the motherboard, a B350 chipset shall be enough for you to start. (Recommending ASUS)
My power supply is a Thermaltake Smart 500W, however you can get a Corsair 430 or 450 if your budget is adjusted.
Regarding to the RAM memory, 8gb in 1x8 DDR4 combination should be OK for now. Upgrade to 16 later if possible.
For the GPU, i'd choose a RX 570.
Storage: Get an SSD if possible, the speed boost is absolutely worth it for such a low price as SSDs have. Your current HDDs seem to be good enough, keep them.
Good luck, happy buying dude!