I am very new to biking haven't truly ridden in years. However due to wanting to get in shape and healthier I am looking to buy a bike. My needs are few, a simple bike to go back and forth to the store, and my work which, is local also preferably something under $200. I am female and 115 at 5'6 and I honestly dont even know what size frame I should be looking for X_X

If i keep up with biking I would want to buy a better bike down the road. Due to living in south Fla I was thinking towards a single gear bike, also I live in the smallest town ever and the only store is a Walmart. A good bike place would be a 2-3 hour drive for me so I dont want to waste time if I dont know what I am looking to buy. I also not knowalgeble to look on craiglist.....

I was looking at the craptastic looking Thruster Fixie as I can repaint it and change out the tires. The reviews I see on it are decent and I think it would be ok for what I want it for but I just dont know. Any help would be greatly appreciated.

P.S love the looks of the old vintage bikes but not enough knowledge to know whats a good deal and what isnt.