Hello, angel eyes. There's no info on your profile to indicate where you are from or what kind of riding you will be doing. If you live in a rural area, a fat tire back would probably be best. If you live in an urban area a CROSS bike (narrower tires but not the real skinny ones) would be best. A good bike shop, as suggested above, will help to fit a bike to your body size -Tall, Short, etc. Your body size determines the bicycle size you need. Be prepared to spend as much money as you can afford and maybe a little more because if you do not get a bicycle that fits you, riding will be a bad experience and you won't stick with it. A properly fitting bike is a wondrous thing. Good Luck! And do not be afraid to ask questions when you are shopping!!!!!
Also be aware that there are certain muscle aches that will occur once you start riding. They are normal and natural and the bike shop can suggest ways to overcome them, or came back here and you'll get even more ways to help alleviate those bothersome pains.
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ljbike