There are 3 problems with that build suggestion: A) that actually reduces his system memory (current system has 16GB); B) RAM should always be purchased in 2-stick kits to take advantage of dual-channel speeds; & C) the RAM speed is way too low, Ryzen CPUs lose performance unless you use faster RAM (should be at least DDR4-2800, if not 3000 or 3200). That adds another $80 USD to the build price at a minimum, so well above his budget.
Although it's not a great upgrade anymore, if he's that limited on budget (as he stated, he can't afford a Ryzen upgrade), he get an FX-8350 or 8370 for under $150 USD (https://pcpartpicker.com/products/cpu/#s=23&sort=price&page=1): increases him from 3C/6T to 4C/8T, & boosts his base & Turbo clocks. And, they're supported by his motherboard (https://www.gigabyte.com/Motherboard/GA-78LMT-USB3-rev-60#support-cpu).