Most .22's are pretty small anyway so that shouldnt be a problem in finding one that fits you well. The ruger 10/22 is hard to beat for a first rifle. I prefer a Marlin model 60 over it myself.
Visit the local gun stores in your area and pick up and hold every thing you can get your hands on and see how they feel to you....
Both of the mentioned guns can be found new for under $225, and picked up used off Armlist.com ( the craigslist of firearms) for about half price.
You dont need a $500+ rimfire to start out with. But ya just might want one in the future