My son is a competitive athlete, so I know something about shoes! Feet are extremely individual - what I need is not what you need.
What I would do is go to a local running store, one that is independently owned. If you go to a chain (like Olympia Sports or Sports Authority), the clerks are not necessarily trained - they push the shoes with the highest profit margins, or what's in overstock, sometimes.
A store geared to athletes will have trained people. They should watch you walk (in just your socks) to see if you pronate and to examine your stride. They might do this outside, or they will probably have a treadmill there that you can walk on. Explain exactly what type of exercise you will be doing, as you have here. They will make sure the shoes have the right structure, support and cushioning. Our local store caters to runners but they extend that knowledge to people who need cross-trainers, tennis shoes, basketball shoes, etc.
The shoes should be guaranteed for a certain period of time, so that if you experience any problem, you can bring them back for exchange.
Spend the money on the first pair. You could spend $100 on 5 pairs of Walmart shoes and have pain & problems. Then, for future shoes, you can either stick with that store (they should be able to examine the shoes for you to see if they still have life in them, from cushioning to the right flexibility) - or, you can try to find them elsewhere or on line for less money.
I tend to give the little store my business, and shop for discounts on my other exercise gear that doesn't matter so much. But a good pair of shoes (and a good sports bra!) are worth it.
FYI they may tell you that shoes with a great tread are not the best for zumba - I'm not sure. I find that I can't spin around in my regular shoes, and I don't think the class forces my feet to take as much pounding as the treadmill does. But you should ask. A lot of it is based on your particular feet.
Our store also extends a 10% discount to athletes on the local teams, and they give me the same discount as my son. Nice deal - you could ask about such programs.
Good luck!