Here's what I posted in a recent thread on the topic....not sure what your budget is but you can spend a few hundred on more expensive sights, or you can spend about $100 on the setup below that will function equally as well, and use the money you saved on ammo.

I've got a Bushnell TRS-25 on a medium height riser with these flip-up BUIS from Ozark Armament. I have right at $100 invested in both combined, and all have performed flawlessly so far. The trs-25 is probably the best "budget" red dot you can get, and those iron sights are great for the price. I originally bought them just to have something on it until I could drop $100 for the Magpul BUIS set, but once I put them on, I'm going to stick with them - no reason at all to replace.

Ozark Armament BUIS