Here is my stock answer for a budget build;
take from it what you will.
------------------------------ 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://community.newegg.com/eggxpert/computer_hardware/f/135081/t/45344.aspx?Redirected=true
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.
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------------