Well, I've never built a computer before...
Building a Hackintosh isn't for the faint of heart nor the impatient, imo. It's a steep learning curve, but not insurmountable. What you may want to do, after you get your parts together (don't forget to get an anti-static wrist strap; watch a YouTube to show you how to properly use it) is to make two UniBeast sticks, one for non-UEFI and one for UEFI. (Hey, if you're going to play to learn, then you might as well learn the right way - so that if you make a mistake you don't get discouraged and can try a different method.) You could install it in Legacy (non-UEFI) mode and if, and when, you get everything working right, you can try the UEFI mode. Or you can jump right in into UEFI mode. UEFI is a steep learning curve in itself.
Don't bother using old USB sticks you have laying around the house. Buy two new USB 2.0 ones. Look at the back of the package - get the ones that come with a 5 year warranty. A lot of them will come with 2 year warranties, some won't even list it on the back. Stay away from the ones that don't even list a 2 year warranty right on the back. They're cheap. And if you so as much as drop 1 bit when you're doing your install it could very well cause the install to fail.
To increase your chances of a successful build you may want to stick to a motherboard with an Intel NIC, get the fastest possible CPU you can possibly afford, buy only memory in single kits. I usually suggest the max the mobo can hold, if only to future proof it and to resist the temptation to upgrade later on. If you're into video transcoding then you'll want the max, which on a Skylake 4 slot mobo is 64GB; if you're into gaming then 16GB is probably sufficient for the time being, but if running a 4K display is your ultimate goal then besides getting a 4G or 6G video card you'll probably want about 32G of RAM. It's not a hard and fast rule, I just suggest that you don't cheap out on the CPU, the RAM and the PSU. For instance, to be able to do Deep Sleep you will need an Haswell Certified PSU. If you're going to make a media centre box, HTPC, then you'll want the best CPU cooler and the quietest fans, and a mobo that has 5.1, 7.1, etc., sound with Optical Out, etc. Some will only consider a mobo that has Display Port 1.2 since it is able to do 4K @ 60HZ, depending on the CPU.
My usual advice is to research every mobo, mem stick, and PSU deeply - by reading user reviews at Newegg and Amazon, doing browser engine searches for the piece of equipment and adding the words "review" and "problems" to it; and if a search brings up a forum for that piece you will want to see what people are complaining about. When you read the reviews start at the bottom rated, the negative reviews, and work your way up. Look at the time posted because a firmware update could have fixed the problem. Since you have never built a PC you probably won't be able to tell what could possibly have been caused by user error. We all have made mistakes...
I usually suggest an ATX board that has at least 2 PCI-E slots, PCI-E X16 and PCI-E X4, no PCI slots, 4 RAM slots. In a micro-ATX I suggest 4 mem slots and space between the right mem fingers and a long video card. Some are too darn close for comfort... Some guys are committed to SSDs, so they may want more than one m.2 slot on their mobos. Some guys are gamers, so they may want two, three or four full length PCI-E slots to SLI video cards. Four full length video card slots are only available on X99 mobos.
Since you have never built a PC you could start by watching some You Tube videos. Just go to YouTube.com and in the search box type "How to build a PC".
Since you are thinking of going ITX, I suggest you install a single 2x16G RAM kit, and get a case where the PSU sits either above or below the mobo, and not directly where the PSU covers the CPU heat sink.
Don't think of just buying the mobo, though; think of it as a combo with the RAM. Some sizes and speeds are not available on certain mobos, so you may be limited to either 8G or 16G. It may not be a problem now, but at work I just installed Sierra on an iMac that can only have a max of 4G RAM. The more RAM you have the less possibility that you will be swapping to the SSD. And if you have enough RAm you can set up RAM disks to run applications in memory, which is faster than an SSD.
