Help Building PC (first time builder)

Some thoughts for you:

1. windows 10 home is current and that is probably what you should buy
The pro version has few benefits for the home user.
But, one biggie for me is the better control you have as to when windows does updates.
Do not buy a cheap copy of windows. A legitimate copy from a reputable vendor will be more than a 10% discount. Plan on $100.

2. Antivirus. There are many opinions, but if you are careful, the free windows defender does just fine.
It is low impact and gets updated by normal windows updates. You can always change later.

3. Buy a case you love. Looks count, you will be looking at it for a long time. I like the looks of the corsair spec series.
My personal criteria is that it have at least two front 120/140mm intakes.
That will supply cooling air for anything.
If it is filtered, your case will stay cleaner.

4. Your main decision is the cpu. I am not a fan of ryzen if your main usage is for gaming. Intel will have faster cores which is what games need most. Ryzen offere many, but slower cores which are good for multithreaded apps like editing.
Budget about 2x the cost of the cpu for your graphics card.

5.
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.

6. Modern parts are going to use DDR4 ram; no real option there.
Buy all the ram you might ever want up front. Adding disparate ram later is not supported by any ram seller.
a 2 x 16gb kit would satisfy most anybody. Speed is not as important as quantity for the most part.
If you are truly budget constrained, a 2 x 4gb kit will let you game well, provided you are not doing much multitasking at the same time.
But, whenever you want 16gb in the future, be prepared to sell your 2 x 4gb kit in favor of a 2 x 8gb kit.

7. On the graphics card, again, budget 2x the cpu cost for a balanced gamer.
You might want to consider using intel integrated graphics initially until this shortage of good graphics cards eases.
You will not play fast action games with integrated graphics, but there are still many games that will do ok.

8. The psu you need will be determined by the graphics card.
Here is a nice chart:
http://www.realhardtechx.com/index_archivos/Page362.htm
550w is probably right.
650w will handle any modern graphics card.
It will only use the power demanded of it, regardless of max capability.
DO NOT try to go cheap on the psu.
Try to buy a tier 1 or 2 unit
Here is one list:
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html
I particularly like the new Seasonic focus power supplies.

If you need wifi, plan on buying a wifi adapter card for a pcie x1/x4 slot with a nice antenna.
A USB wifi dongle can work, but they are weak.

9 . Do not go overboard on a cooler, particularly if you do not buy an overclockable processor.
I might suggest planning on a cryorig H7 for about $35.

10. FWIW:
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.
3. If your motherboard does not have a PWR button, momentarily touch the two pwr front panel pins
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.
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.

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.