First, you have to make a choice on whether or not you wish to become completely dependent on Optical Sights. BTW, at 61 years of age I've become so far sighted that the sights on a handgun or rifle are always blurry for me unless I "cheat" and shoot with reading glasses.
I also have a precision AR that was rather expensive to build and is 1/3 MOA capable on days when I am really shooting well. My primary use for this rifle is to challenge my ability by attempting to achieve hits on 1/2 diameter stickers at 100 yards. Naturally this rifle is equipped with a good rifle scope that I've spent a good bit of money for and time using. One thing I've discovered is that even with a good sight set up correctly your eyes will get tired and you will then have difficulty simply seeing the crosshairs. Point is here that Optics aren't a perfect solution, especially for those of use getting a bit long in the tooth.
I actually spend most of my time shooting with iron sights and doing it without even the aid of reading glasses. Because I have learned that by constant practice I can maintain my ability to shoot pretty accurately with sights that are rather blurry. BTW, the aperture in a rear peep sight can actually help with blurred vision if used properly. Because if you peer through a small aperture it will increase the "depth of field" of your focus just like using a smaller aperture on a camera lens will. The "trick" here is to place your eye as close to that rear peep sight as is possible. What this means that a rear peep sight can serve the same purpose as reading glasses without using any glass. Which is why this old fart can still shoot with irons with a fairly high degree of accuracy. BTW, on a very good day that means 1 inch five shot groups at 100 yards from a rest and on a more average day somewhere around 1 1/2 inch groups.
Point here is Iron Sights can still work, even for those who need to stand on a chair to see a menu at a restaurant. However, maintaining the skill to do this requires PRACTICE and that is why I stated that the use of Optics can make you DEPENDENT on Optics.
Now, some tips. First, a dab of white paint on a front sight post can make a HUGE difference of you are shooting at a black target. If you are shooting at a small dot on a white paper plate or something similar you'll want to leave the front sight post black. Second, with the standard Military style aperture sight arrangement you want to place the rear peep sight at a distance where the outer ring will coincide with the "wings" on the front sight. This will aid in keeping the front sight post well centered in the aperture, which is the KEY to shooting accurately with this style of sight and why PRACTICE is so important. The key to accurate shooting with any type of iron sight on a rifle is getting your eye positioned exactly the same every time you sight the rifle. Which is why a round rear peep sight is so advantageous. However, even with a peep sight there is still room for some misalignment so IMO using iron sights can be a "use it or lose it" proposition.
Some additional things to consider. I have reflex sights for both of my 16 inch AR's and 3 of my revolvers. While I don't use them a lot they are a useful type of sight to use for accurate results out to about 50 yards. The reason I don't use them a lot is because I feel I could become too dependent on them. A big plus for reflex sights is that they are nearly weightless. BTW, that 20 inch precision AR of mine weighs in at a bit over 11 lbs. with the scope mounted and that scope is NEVER removed for fear of disturbing it's sight alignment. My 16 inch AR's both come in at just a bit over 6 lbs. with iron sights. When I wish to shoot the shorter rifles with Optics for load developments or simply a break from irons I have a 2-8x40 cheap scope in a Burris QD mount or a dedicated reflex sights in a QD mount. Note, I've found that a QD (Quick Detach) mount will typically repeat the sight alignment within about 1/2-3/4 inch at 100 yards with is plenty good enough for me to see if a particular new load shoots up to snuff. I also have folding Magpul sights front and rear on my 16 inch AR's, so I can fold them out of the way if I'm going to shoot with optics, however each QD reflex is set to a center co-witness with the irons for two reasons. One is that it allows me to double check sight alignment and the other is so I can use the same cheek weld with either sight. BTW one of my shorter AR's is a 300 Blackout and the other is a 223 Wylde (an accurized chambering for either 223R or 5.56 Nato). By happy coincidence my most common load for the 223 is only 2 ticks different in elevation at 8X than what I typically shoot in the 300 BLK so all I have to do is use a different tick in the crosshair on that QD scope setup when using the scope. I'll also note that the Burris PERP scope mount IMO is well worth the 130 bucks I paid for it when it was on sale. Height of the scope is dead on perfect for my cheek weld on the butt stock on either AR and it actually repeats very well for a detachable mount.
Finally, spend time thinking about what you want to do with your FIRST AR. Because the AR15 is such a flexible platform you really can't have just one and because it is real easy to get really expensive with all the bells and whistles available for an AR. BTW, on my precision rifle the barrel and scope alone totaled at just north of 1000 bucks and I went relatively "cheap". If you want a single point rifled barrel that doesn't start stringing shots as it heats up you can expect the cost to start at 5 grand. Then there are the various high end scope systems out there that can make your jaw drop with the cost. If you want a rifle for short range plinking at 100 yards or less I think it would be hard to beat the M&P Sport II and maybe 2 bucks spent on a bottle of Testors model paint at a hobby shop. Speaking as someone who has hand built every one of his AR's using premium components I have to tell you that every time I see the Sport II on sale at a bargain 600 bucks I am tempted to pick one up simply to use a range "beater" I can just throw in the trunk for days when I have a free hour or two.
