My $0.02
Bushnell TRS-25 is a great value, and a very light weight unit with a bright dot. Downside is the dot is not especially crisp, so accuracy work is more difficult
Bushnell 730132P "trophy" 1x32 AR optic is another decent option for ~$100. I like the T-dot reticle, and I like the built-in pistol type sights for applications which have no iron sight provision, such as my 7.5" SBR.
On the very low end cost-wise, the UTG 3.9" sight (~$50) is actually a decent little unit, with a nice clean reticle and lockable turrets. I have one, it has held zero and always stays on (sometimes an issue with cheaper RDS). It does use a different button cell than the standard CR2032, though. 1620, IIRC.
All of those, of course, I'd consider plinking sights. I wouldn't want them on a rifle that's gonna see really had use. That's what Aimpoints are for.
Not quite as budget friendly, but the Burris Fastfire micro sights are also pretty good. The Fastfire III is down to about $220 these days.