Is this a good budget pc build?

Solution
The build is reasonable.
He budgeted about 2x the cost of the cpu for the graphics card.
That is a good ratio for a balanced gamer.
You should have a case, personal preference, what looks good to you is ok.

One likely mistake is the ram.
8gb is fine, but it should be a 2 x 4gb kit to run in faster dual channel mode.
And... ryzenn is picky on ram.
Verify that the kit you select is explicitly supported on the motherboard ram VVL list or by the ram vendor.
Not all DDR4 ram is supported.

I think for gaming, intel 8th gen is better. Mainly because of the better single thread speed.
I3-8100; use the included cooler.
H310 or B360 based motherboard.
2 x 4gb DDR4. any speed is good for intel.
I like nvidia graphics for the lower power...
Yeah your cousin is kinda all over the place on parts and picked a terrible PSU as well as setting you up with single channel RAM, here's a better Ryzen build.

PCPartPicker part list: https://pcpartpicker.com/list/cY94Bb
Price breakdown by merchant: https://pcpartpicker.com/list/cY94Bb/by_merchant/

CPU: AMD - Ryzen 5 2600 3.4GHz 6-Core Processor ($165.99 @ Walmart)
Motherboard: ASRock - B450M PRO4 Micro ATX AM4 Motherboard ($81.98 @ Newegg)
Memory: Patriot - Viper 4 8GB (2 x 4GB) DDR4-3000 Memory ($74.99 @ Newegg Business)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($43.89 @ OutletPC)
Video Card: EVGA - GeForce GTX 1060 3GB 3GB SC GAMING Video Card ($215.60 @ Amazon)
Power Supply: Corsair - CXM (2015) 450W 80+ Bronze Certified Semi-Modular ATX Power Supply ($49.88 @ OutletPC)
Total: $632.33
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-08-06 21:44 EDT-0400

You could swap teh GTX 1060 back for the RX 570 but the 1060 is a faster card, not by alot but still. I'm a Nvidia fan boy but I doubt you will see much of a difference between them unless the game you are playing is more optimized for one over the other. So up to you.
 
The one I built for you is a a great mid range computer. The only thing I left up to you is, Case, Operating System (id suggest buying the retail copy of Windows 10 Home and not the OEM version of it), and any peripherals you want. The graphics card choice, 1060 vs 570 is entirely up to you, as they are similar in performance however the EVGA 1060 I chose for you comes with EVGA excellent customer support.

One Last thing to keep in mind when you choose a computer case typically the budget motherboards will be Micro ATX (mATX like the one in the Ryzen build I made) for factor, that means although most larger cases will support them no problem, may have to move the standoffs you will have the option to get smaller mATX cases if you want.



PCPartPicker part list: https://pcpartpicker.com/list/9HRrYT
Price breakdown by merchant: https://pcpartpicker.com/list/9HRrYT/by_merchant/

CPU: Intel - Core i5-8400 2.8GHz 6-Core Processor ($178.99 @ Amazon)
CPU Cooler: Cooler Master - Hyper T4 70.0 CFM Rifle Bearing CPU Cooler ($16.99 @ Newegg)
Motherboard: MSI - B360M PRO-VH Micro ATX LGA1151 Motherboard ($63.99 @ Amazon)
Memory: Patriot - Viper 4 8GB (2 x 4GB) DDR4-3000 Memory ($74.99 @ Newegg Business)
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($43.89 @ OutletPC)
Video Card: EVGA - GeForce GTX 1060 3GB 3GB SC GAMING Video Card ($215.60 @ Amazon)
Power Supply: Corsair - CX (2017) 450W 80+ Bronze Certified ATX Power Supply ($23.98 @ Newegg)
Total: $618.43
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-08-06 22:20 EDT-0400

I managed to find a cheaper power supply for this build, it would also work on the Ryzen one, so if looking at price comparison keep that in mind. Although its not modular like the CX450M so youll have to tuck whatever cables you dont use someplace if you don't want to see them.
 
The build is reasonable.
He budgeted about 2x the cost of the cpu for the graphics card.
That is a good ratio for a balanced gamer.
You should have a case, personal preference, what looks good to you is ok.

One likely mistake is the ram.
8gb is fine, but it should be a 2 x 4gb kit to run in faster dual channel mode.
And... ryzenn is picky on ram.
Verify that the kit you select is explicitly supported on the motherboard ram VVL list or by the ram vendor.
Not all DDR4 ram is supported.

I think for gaming, intel 8th gen is better. Mainly because of the better single thread speed.
I3-8100; use the included cooler.
H310 or B360 based motherboard.
2 x 4gb DDR4. any speed is good for intel.
I like nvidia graphics for the lower power requirement. GTX1060. the 6gb version if you favor fast action games.

A 550w psu will power anything up to a GTX1080.
I like the Seasonic focus line.
Do not go cheap on the psu.


I will never again build without a ssd for the "C" drive. It makes everything you do much quicker.
120gb is minimum, it will hold the os and a handful of games.
But, many things default to the "C" drive.
When a SSD nears full, it will lose performance and endurance.
240gb is the recommended minimum.

If you can go 240gb, or 500gb you may never need a hard drive.

You can defer on the hard drive unless you need to store large files such as video's.
It is easy to add a hard drive later.

Samsung EVO is a good choice for performance and reliability.








 
Solution
The motherboard in the original build has 4 memory slots. So get 2x4gb now, you'll still have two open slots for future memory sticks if you need to add them. Otherwise it looks good to me. One thing I'd do if this were my choice, I'd use the stock cooler for the CPU and spend the money on a 120gb SSD. Even a cheap Sandisk Ultra would be worth having for a boot drive.
 
One other potential issue I see with that initial build is that an A320 motherboard won't allow for overclocking, while Ryzen (non-X) processors tend to offer more competitive performance with an overclock, and also with faster RAM, which doesn't cost much more.

And it's also possible to find some Radeon RX 580 4GB cards for about the same price as that 570, which should be a bit faster than either an RX 570 or a 1060 3GB...
https://pcpartpicker.com/product/XYDzK8/asus-radeon-rx-580-4gb-dual-video-card-dual-rx580-o4g