Whatever is the most comfortable. A pair of $35 sneakers from Kmart works for me. Make sure you get the ones made with real leather, as they last a year or more. The $25 vinyl ones wear out after about a month.
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I don’t think you need any specifin brand because if so then I am guessing that you won’t be able to find anything under $100.
I suggest going to your local stores and malls to look in every store/shop and see if you won’t find something that you like and for a good price.
Whatever is comfortable and is of quality. There are many good brands out there. Depends on your preference really. There are some good quality shoes under $100 but they are usually over $50. Depending if the store has a sale or not. Look for quality and longevity. Do some research and find a pair of shoes that works best for you. Good luck!
In line with @Blondesjon‘s response, I would only get shoes that are designed for “Left” and “Right” feet (one of each). And I know this is just the middle-class conformist in me, but I prefer shoes that match, too, in size, style, color and feel. But don’t let my reactionary ways put you in any kind of fashion strait jacket.