Red Dots, Magnification, and Rifel Scopes?

I am looking for an aiming device, I am not sure what kind though.

The farthest I will be targeting is around 300 feet.

I am wondering if I should get a red dot sight such as this Docter or this

or if I should get this 2x red dot

or if I should get a rifle scope and mount the red dot over top of it.

It would be nice to have something like the ACOG with red dot but I just can't afford it. Even better would be an ACOG with an EOTech on top of it

I am leaning towards one of the red dot options, I don't think I need a riflescope for what I will be using it for.

A red dot is fine for 100 yard shots. It's up to you to determine if you want the accuracy a fine aiming point like a crosshair offers, or if a dot that takes up several inches at that distance will suffice. For precision, a red dot is not the correct choice. To hit a pie plate quickly, a red dot works well.

Thanks for the reply Steve

I am going to get one of the open/tubeless sights, maybe that NCStar. I might pick up the 2x one just to mess around with.

Just curious, do ACOGs have good eye relief? Do you still have to mess around with parallax settings and such?