I love doing craft shows! Whether or not you make money is a bit of a crap shoot though. So much depends on factors you can't control, like whether there are a lot of people come through, are they buyers or browsers, the weather, etc.
I've done shows where the tables cost anywhere from $25 to $65. The more expensive tables have been at larger shows or shows that were held in support of a hospital or other good cause.
It helps if you have actually attended the show yourself as a potential customer before signing up to do it, but how many of us actually do that (not me). If you know anyone who has done the show before, you can ask them about it - just bear in mind that you may make something entirely different from them, but it will give you the feel of the show and more importantly, the clientele.
I agree that having the Square is a very good idea. I had it this year and picked up a few sales, including a large one, that I would not otherwise have gotten and it made the difference between making money and losing it at a couple of shows.
One thing I have found is that most people who attend are looking for small ticket items, $5 to $15 or $20. Taking a broad range of price points is a good idea, but I would bring a larger quantity of the smaller priced items. It's amazing how quickly those sales add up. A wise person once said that it is easier to sell 5 $10 items that to sell 1 $50 one.
As for quantities, it depends on the price points and what you make. I sell jewellery, accessories and artwork. I tend to take over 500 pairs of earrings to a show and up to 100 of each of the other lower price point items. For anything above the $20 price point, I may only take 5 to 20 of each. It is better to take too much with you than too little. Show organizers take a dim view of people who pack up and leave early because they sold everything before the end of the show. You may not be asked back or if you do apply, you may not be accepted.