A few years ago a mini bag meant one thing, a tiny shoulder bag that held a card and a lip balm and absolutely nothing else, carried because it looked good and not because it did anything. That's changed, and for the better. The better ones now come with a cross body strap, an actual zip, and enough room for a phone, which was always the one thing the early versions couldn't manage. Progress, of a sort.
This is not an everyday work bag, and I'd be lying if I said otherwise. It's for the evening after work rather than the day itself, for the wedding where you need your hands free, for a meal out, for anything where you're not also carrying a laptop, a water bottle and whatever got left in your bag from three Mondays ago. It sits well with a plain dress or a simple top and trousers, something that isn't already busy, because the bag is doing enough visual work on its own. If you're starting from nothing, go for a cross body in a neutral, black or tan, rather than a clutch style or anything with a top handle only, because the strap is what makes it usable rather than just photogenic sitting on a table. You want one with a strap long enough to actually go across the body and not just dangle at your hip looking indecisive. Check the stitching round the strap attachment point before anything else, that's where cheap ones fail first, usually within a few wears, and it's not a repair anyone's doing for you. Run a hand over the zip, a good one glides, a bad one catches and you'll be fighting it in a car park with your phone in the other hand. Press the corners too. A proper mini bag holds its shape when it's empty, a disappointing one collapses in on itself like it's given up for the evening before you have.
I took one through a week once thinking it'd replace my usual bag and by Wednesday I'd given up and gone back to something with actual pockets, which taught me this isn't that kind of bag and was never trying to be. Fine. It has a different job. Reach for it when you're going out rather than just going somewhere, when you want your hands free and you've already decided what you're not carrying.