I was a little intimidated the first time. I actually bought one off the shelf first because I was afraid to try to build one. After messing with it for a little while I started buying stripped lowers and figuring it out. It is not difficult and there are a million videos on line that will show you exactly how to do it. You could spend a little more money on "Kits" which have most of the stuff you need or you can buy individual parts. Most likely whatever lower parts kit you buy you will end up changing a few things. Trigger, Buffer/tube, maybe you want an oversized or ambi safety or bolt release, etc.. I'd keep it simple for the first one. You can always easily swap those things out later.
I suggest buying a complete upper the first time too. I don't think building one is any more difficult than doing the lower, but messing with gas blocks and tubes and all that is a process all it's own. For the first one I would skip it and just buy a complete upper receiver. Several decent ones at affordable prices. Aero is a mid tier option, Bravo Company might be a little higher end, but also considerably more expensive. Many of those companies use the same barrels made by Faxon and others. A really affordable upper is Bear Creek Arsenal. They get mixed reviews on line and I certainly wouldn't rank them up there with high end stuff, but I have two of them, I paid under $300 for them and have ran the shite out of them with no issues. Accurate and reliable they are. My next one will likely be a BCM ( Bravo Company). As for lowers I totally agree with Hans. As long as it's in spec they are all about the same. You can get an Anderson stripped lower right now for about $50. I have two and they are both just fine. I also have a PSA stripped lower which is also fine.
You could rush out and buy a bunch of tools, but unless you plan on doing a bunch of them I wouldn't because you don't really need most of that stuff. You can do without a wrench for the Castle nut, , but that is the one thing I would buy if you can't borrow one from a friend, which is what I did. NC Star sells one for about $20. You will need a set of regular punches and I would suggest getting some roll pin punches too, but I built my first one without them. Punches are cheap and you can get them from Harbor Freight or Lowes or wherever. No need for anything fancy. I would also spend about $12 on a full set of T handle hex wrenches too. You can easily make your own armors bloack out of a scrap piece of wood. You definitely will want to use one when you're installing the trigger guard roll pins. All this stuff is explained in pretty good detail in most videos. I'd skip the vice blocks, again unless you plan on building several more. They are handy and I did buy one, but not until after I already built 3. I bought a Wheeler lower vice block for under $20. I also bought a small Wheeler screwdriver set for under $20, but you can find the tips you need in just about any cheap screw tip assortment set. And for ARs you rarely use a screwdriver.
Anyway, feel free to ask advice here while you are doing it. I did. These guys are great about it. And here is a pretty good tutorial for building a stripped lower.
Don't want to mess up? Learn how to build an AR-15 lower receiver with 80+ pictures, tricks I learned the hard way, and recommendations of the best parts.
www.pewpewtactical.com
And much as with the story for its automotive equivalent, this is one where there's a lot of good, technical debate.