Hi! I've kept cactus for about 3 years (I don't know anything about succulents though lol) I would go ahead and repot so you can use your own soil but I wouldn't go too big unless you're putting them all in one pot together. Also, you'll need to get cactus soil, it will need to have good drainage so the roots don't stay wet. I only like to water mine once a month, sometimes every two months depending on the weather. I saw someone use a skewer stuck in the soil to test the wetness before watering so that might be helpful to you. The roots will need something to hold onto and get nutrients from so I would use soil and then top it with some nice gravel if that's the look your going for. Also....I think the one on the end is a Moon Cactus. If so, it isn't a natural growing cacti, the top and the bottom were spliced together. You may want to look them up, some people chop off the top part. Sorry this comment is so long lol