Get a Bounty Hunter detector for starters. They have them at Wally World (Wal-mart) and some larger department stores. Matt also sells the here. There are a few different models. Check them out and pick one that you can understand. They start around a hundred bucks or so. You want one that you will be able to take full advantage of the features so you can get the most out of it and then move up to better and more advanced models. The top of the line detectors are the deepest signal machines and are for the really old coin and valuables finds.
I have a buddy that got a Bounty Hunter for his daughter. The detecting bug really didnt bite her and she lost interest, so he uses the thing and cleans up with it! His old coin finds are amazing! For beginners IMO the Bounty Hunter Machines are the way to go.
Check one out and read the manual over and over until you understand it and then try it in your yard or bury coins and try the machine over them to get the hang of it.
If you have any questions just ask and i will try to help as best as i can. Its a fun hobby and can be quite rewarding
Good luck and keep us posted