Do you want a magnified scope or a Red dot? For a Red dot sight(RDS) the two best options are Aimpoint and Eotech. The model will depend on your budget. If you are on a tighter budget, a Bushnell TRS or a Vortex should fit the bill.
I would suggest a quality non-magnified RDS first to learn on before moving on to magnified scopes. Better yet, master your iron sights first then your prefered optic.