There are many sight options on the market today. There are simple peep sights, night sights treated with luminant substances, lasers (both green and red), scopes or magnifying sights, and red dot holographic sights.
The red dot sights are a quick way to place the barrel on target in many cases. The sight has a lens on which is projected a red dot or cross hairs. If it is properly sighted, the red dot on target allows you to put rounds on target very quickly. It does not adjust for clarity and has very slight wind and elevation adjustment.
Many of these sights have adjustments for intensity and allow you to adjust the time the sight is active to conserve battery life. That is a signal for me to remind you that anything you take into the field that takes batteries, can and will fail at some point. Having spare batteries can be a pain, but surely beats having your new red dot sight unavailable.
Holographic sights are available available from discount distributors and are easy to mount on a gun with a picitanny rail system. If your gun does not have a rail system, adapters are available either to replace the scope for your rifle or to mount on top of the receiver.
You get what you pay for, but spend a little time comparing the features and capabilities. There is no need to spend $ 500 on a new system that is night vision compatible if you do not hunt at night. Many of the models look the same, but the controls and battery compartment are in different places. Look to find one that will work for you.
You need to spend a little time at the range to make sure you and the rifle are lined up. You need to sight your new system and you need to practice so that it does not surprise you when you need it during a hunt.
Remember: A red dot sight can solve some of your sighting problems, but it is not magic.