Building your own is not difficult or risky if you read the instructions and do not force anything.
For what it is worth, here are two stock bits of advice:
------------------------------ budget build ---------------------------
For a budget gaming build, I like to recommend that one builds for future expandability.
That means paying a bit more up front for some parts that allow for an easier future upgrade.
A good rule of thumb is to budget twice as much for the graphics card than for the cpu.
Let me start where you might not expect:
1. Buy a good 450-550w psu or better. A quality 450w will run a card as good as a GTX1060 or possibly a GTX1070
Future graphics cards will be built on smaller 14nm so they should not need more power than today.
Look for a tier 1 or 2 quality unit on a list such as this:
https://linustechtips.com/main/topic/631048-psu-tier-list-updated/
Seasonic is always good I particularly like the seasonic focus line:
This 550w unit is often on sale.
https://www.newegg.com/Product/Product.aspx?item=N82E16817151203
2. Buy a lga1151 Z370 based motherboard. About $100.
Do not begrudge paying a bit more now forZ370 which enables the upgrade to much stronger K suffix processors.
3. I suggest a I3-8100 About $120.
In time, you can upgrade to any 8th gen I3/I5/I7 cpu that you want and market the original processor.
If you are truly budget constrained, the Intel G5400 is about $65.
4. The intel stock cooler will do the job.
5. For ram, speed is not important. Buy a 8gb kit of 2 x 4gb DDR4
About $90. If you ever want 16gb, buy it up front in one kit; adding more ram is never guaranteed to work.
Heat spreaders are marketing and generally useless.
6. Cases are a personal thing. Buy one you love. Most will do the job for <$50.
Here is a silverstone PS08 for $50; It fits a smallar M-ATX motherboard.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163223
7. The graphics card is the most important component for gaming.
I think a GTX1050 or GTX1050ti would be appropriate, plan on $120-$150.
You could go stronger in the video card if your budget permits and your games need it.
I like EVGA as a brand. They have a 90 day trade up program if you find you need something stronger. Read the fine print on the program.
On the other hand, you could build using the integrated 630 graphics which is quite good and see how you do.
By deferring on the graphics card, you will get a better idea of what you really need.
Integrated is fine for sims, but not fast action games.
8. Lastly, I will never build again without a SSD for the "C" drive. It makes everything you do so much quicker.
Buy a samsung evo of 240gb or better; about $90.
I think this totals about $600.
-------------good luck------------
MY build process:
Before anything, while waiting for your parts to be delivered, download
and read, cover to cover your case and motherboard manual.
Buy a #2 magnetic tip phillips screwdriver.
1. I assemble the critical parts outside of the case.
That lets me test them for functuonality easily.
A wood table or cardboard is fine.
2. Plug in only the necessary parts at first. Ram, cpu, cooler, psu.
Do not force anything. Parts fit only one way.
Attach a monitor to the integrated motherboard adapter if you have one, otherwise to the graphics card.
3. If your motherboard does not have a PWR button, momentarily touch the two pwr front panel pins with a flat blade screwdriver.
4. Repeatedly hit F2 or DEL, and that should get you into the bios display.
5. Boot from a cd or usb stick with memtest86 on it. memtest will exercise your ram and cpu functionality.
6. Install windows.
7. Install the motherboard cd drivers. Particularly the lan drivers so you can access the internet.
Do not select the easy install option, or you will get a bunch of utilities and trialware that you don't want. Drivers only.
7. Connect to the internet and install an antivirus program. Microsoft security essentials is free, easy, and unobtrusive.
8. Install your graphics card and driver if you tested with integrated graphics.
You will need to remove the graphics card later to install your motherboard in the case.
Make a note of how the graphics card latches into the pcie slot.
The mechanism will be hidden under the card and may be difficult to work if you have not previously checked how.
9. Update windows to currency.
10. Only now do I take apart what I need to and install it in the case.
11. Now is the time to reinstall your graphics card.