What caliber are we talking here?
The biggest advice is have realistic expectations for accuracy. Semi-auto rifles are generally more difficult to shoot accurately that bolt guns. I would be happy with 1-1.5 MOA at 100yards groups unless the rifle comes with some kind of accuracy guarantee.
For some reason I found .223 semi-autos (BCM MK12) to be less accurate than .308 (LMT MWS). Perhaps it's because I haven't found ammo that the rifle really liked. My LMT .308 does really well with FGMM 168 grain.
I strongly recommend getting a quality tripod regardless of the rifle being used as it opens up a lot of versatility.
I also don't like Magpul PRS Gen 3. I find it too long in the shortest position. If you really want a "precision type stock", I would recommend LMT DMR Buttstock. However, I found regular AR stocks work well. If using standard stock, I tend to prefer Magpul ACS because of the weight and having the lock mechanism covered so you can't accidentally depress it with the support hand unlike VLTOR stocks.