Rebuild my PC

[PlayToy]

This is the specs of my crappy desk top ....

Operating System
Windows 10 Pro 64-bit
CPU
AMD Phenom X4 9100e
Agena 65nm Technology
RAM
6.00GB Dual-Channel DDR2 @ 399MHz (5-5-5-18)
Motherboard
Gateway RS780 (AM2)
Graphics
DELL 1907FP (1280x1024@60Hz)
1024MB ATI AMD Radeon HD 7700 Series (VISIONTEK)
CrossFire Disabled
Storage
596GB Western Digital WDC WD6400AAKS-22A7B2 ATA Device (SATA)
Optical Drives
ATAPI DVD A DH16A6S ATA Device
Audio
Realtek High Definition Audio

I want to rebuild it and don't know where to start, i know i should keep the power supply and SSD but what else to save and replace. I'm pretty sure i should start with the mother board and go from their. I want something affordable, dependable and pretty basic. Where to start and look for, If anybody has some suggestions it would be appreciated.