First I would suggest going to a reputable archery shop. It can be hit and miss with big box stores like Cabelas and Bass Pro. Get fitted for a bow. Dont buy 2nd hand unless you know what you are getting into. An incorrectly fitted bow will cause nothing but frustration. I got my daughter a Diamond Infinte Edge. Look at the adjustability of both the draw length and the poundage. She started shooting before she was 12 and is pretty damn good. As she grows and her muscles develop we can increase the bow to fit her.
Dont get caught up around FPS and poundage. If you dont know how to shoot a 70lb bow that shoots 350FPS will only cause you to miss faster. The arrow is not going to outrun sound so worry about shot placement not speed. For a hunting situation I would reccomend you set the poundage down to a leve you can control when the world goes to hell. I test mine by sitting down on a stool, lifting my feet off the ground and then drawing the bow without having to raise it up or down and then slowly let the bow back down. If you are struggling holding still it is to much weight. If your area lends more to ground stalking you might be able to get away with a little more poundage but down here most deer hunting is from a blind or a tree stand and the more movement you have the more likley you are to get busted.
Mind the wind. It wil help you and it will screw you, and can do both in a matter of seconds. Remimber with archery equipment you are as close as you are going to get to thier face and than means thier nose.
The number of arrows you shoot in practice is not nearly as important as the quiality of the shots you take in practice. Start with a normal target then move to more of a 3D set up. Looking at a set of painted in vitals that are square to you is much different than looking at a 3 dimensional target. You can move a 3D target around and take shots from different angles. Remimber its not where the arrow hits, its how it tracks through the vitals that is important. A steep enough angle might make it look like the shot is to far back but follow the shaft through the body and see if it connects with something vital. Heart shots are great but double lung at a minimum is what you want. Get both lungs. An animal tha cant breath cant run to far.
Learn to fletch your own arrows, its like reloading but a hell of a lot less expensive. I wrap mine with a very bright color and it makes it easier to track with my eye or to find if I miss.
If you can practice at a distance 2 times more than you think you will get a shot. Last year I was practicing all the way out to 80 yards. I would shot 6 arrows from 40 every 10 yards out to 80 and then every 10 yards back in to 20. The max I will take a shot from a tree stand is 30 unless conditions are perfect then I might stretch it to 40. But it is fun as hell watching an arrow with one second flight time hit a 3D target from almost 100 yards away.
Have fun with it. Archery is one of those sports that you can involve the entire family. There is something about the flight of an arrow, especially when it goes on target that is mystical.
Pocket range finder. You will eventually make it up to that 70lb and 280+ speeds but even there the difference between 30 and 35 yards can be a wounded animal.
It may sound like a lot but it all falls into place quickly. I can assure you that once that deer steps out at about 20 yards and you swear he can hear your heart beating, as you draw back you will be shaking like a dog trying to shat a peach pit, you will know why so many people love the bow hunt. It is a rush like no other. Then it will be on to bigger animals. Last year was my first elk hunt, it was archery and I didn't have a tag so I was just calling for the guy that did. When that bull was 40 yards from me and I didn't even see him I thought I was going to have a heart attack. It is addictive. While I still enjoy the muzzle loader and gun hunts they do not match the sheer rush of the bow hunt.
ETA: Here is a link to the bow I got my daughter. If there isnt a Cabelas or Bass Pro near you, it cal always be ordered.http://www.cabelas.c...vw&gclsrc=aw.ds
With this package all you really need to add is a release, some arrows and practice and hunting heads.