What is your primary planned use for this rifle, and what distances will you primarily use it at?
Aimpoint is always a good pick for unmagnified optics, the Aimpoint PRO is typically the most affordable model and can be had for pretty decent prices, with T1/T2 or H1/H2 being good options toward the higher price range. Trijicon MRO is another one to consider, as well as Eotech XPS or EXPS series sights. These work really well for sub-100 yd and CQB type engagements, but are certainly capable well past that, especially if paired with a 3x magnifier.
Trijicon ACOGs (very pricey unless you find a nice used deal), or something like a Vortex PST 1-4x24 (SWFA also makes some decent mid-range glass). These options would cover a Recce-type rifle, from unmagnified 1 power up to 4 or 6 power for more accuracy at 200+ yd engagements.
If you are looking for a distance or precision setup, check out Vortex PST series (4-16 power range) or SWFA SS scopes. I recommend running offset irons with these, such as Dueck Defense RTS sights.