Scopes don't make you, or your rifle any more accurate. With good quality iron sights you are able to shoot quite well at longer distances, as long as you can clearly see the target. In bright light, on a firing range this is fairly easy.
A scope purpose is to make it easier to see your target, especially in poor light, or if the target is partially obscured as in a hunting or military situation. Even a non magnifying optic does this. Most dot sights are meant to make it quicker to get on target up close, not for precision shooting.
I like a low powered 1.5-4X or 2-7X scope for all around use. At the low powers they are quick on the target and provide almost the same field of view as the dot sights, and are actually quicker than using irons. Adjusted up to the higher powers they make it easier to see your target.