Welcome to the sport of cycling! Good shorts will prove valuable. There are many to choose from and most people I ride with have their own preferences. I favor Pearl Izumi Attack shorts. They run $70+ but I often get three or four seasons out of a pair before they have to be trashed if I rotate them. I usually rotate between three pairs.
Jerseys are nice for the pockets but the best reason is for sweat wicking. You can get the same effect with any polypropylene shirt from the Dick's. Cotton Tee shirts will soak up the sweat and be uncomfortable. As far as the body image questions, I gave up caring long ago. Don't get me wrong. I want to look good and will as I loose weight but I'm not waiting until then to wear comfortable cycling clothes.