Like all things in life, good, bad, and great are all relative terms, meaning different things to different people. As an artist that could not be truer. When another artist ask you if you had a good show, you will usually only answer yes or no, unless you have a much longer conversation to define what good really means.
As a new artist starting out your goal is likely to make back your costs to be at the show, ie application and booth fees, gas, any lodging fees, etc. Of course any artist you speak to will want to make a profit too, though when you are first starting out there are many unknowns, so while you want to make a profit, you understand that it takes time to consistently make a profit. Even as a seasoned artist, you will still have shows in which your sales do not cover your costs. Though as you do more shows, you start to learn more and can hopefully minimize those shows.
Starting out it takes time to figure out which of your pieces are the most popular, what format they sell best in, which market is your market in regards to the region of the state or country. While you are figuring out your market, your stages of success, and what defines a good show will change.
There are outdoor show artists that will tell you that the formula for a good show is to make 10x the cost of the show or booth fee. Other artists have told me that they are happy to engage customers, cover their costs, and make a small profit. For me personally, I want all of it. I want to engage with customers, cover my costs, and make a profit.
While there is no formula that I have found to tell an artist how to do this, one thing is certain. It will be different for each artist. A show that I make a profit at and engage customers, maybe a show that another artist does not cover their costs. Each medium of art is different for sales and shows. The best way to figure out your shows and your market is to try a show once. If you do not do well, then you can make a note not to do that show again. If you find your next show was not good, then you can compare the two shows that were not good. You can see if they have similar traits, ie they are shows in coastal towns or they were both shows at music festivals. If the shows had similarities, then you can make a notation and use that information for future shows.
So to answer the question, what is a good show? There’s really no right answer for any artist. You go out, you try new things, be open to making adjustments, keep track of all of your sales, and strive to keep getting better. The sales will come if you can do all of the above.