You'll want something with a lot of support - which, in general, you can only get in athletic shoes. There are tons of them for under $50. Try to find a pair of running shoes with thick soles.
Birkenstocks are very comfortable for long hours on your feet. They even have professional styles for nurses, food workers and others who are constantly standing.
Wear Dr. Scholl's Shoes. They are the best. I wear them to school. You can wear Nike gym shoes, any gym shoes really. You can by Dr.Marten shoes as well. They are very expensive, but I fancy them. I actually own a lot of them. They're worth it. Sketcher is the cheapest I can think of. If anything, you should buy a good pair of expensive shoes that are actually worth buying. Its better to buy 1good pair of expensive shoes than to buy lots of cheap gymshoes, given the fact that if they are cheap, they will break easily and you will never stop buying shoes. Go to Ross or something.
Well, they aren't gym shoes, but Toms are so comfortable! I wear mine all day and they never hurt. They are usually $55 and a lot cuter than gym shoes..
Lady Footlocker often has many sales in shoes like Nike, Rebock, and Adidas. Payless also has great deals.