A really basic but very necessary skill in tumbling, also performing in cheerleading, would be your round off. It is similar to a cartwheel in the sense that you start it just like a cartwheel, but the ending is what makes it a little different. A cartwheel you would keep your legs separated, and in a round off, you would aggressively bring them together and land on two feet. Coming out of this skill, coming out of the round off, most kids or most athletes performing in gymnastics or cheerleading would do either a back handspring or a back tuck, which leads to other skills.
The easiest way I have found to do it is I always use some chalk to draw out where I want the feet, where I want the hands, how to do the hands when you put them on the floor, and where to put your feet. There are numerous different drills that I have acquired over the years that I use on my athletes, and most of them have to do with a cartwheel or snapping out of a handstand onto both feet aggressively.
You want to make sure when you land though, you do want your arms up, you do want your core to be tight, and you want to make sure that you're not leaning so far forward. A good way to do this would be to do numerous cartwheels, cartwheel step together, where you would land on one foot first, pull the second foot in, and that would simulate how you're going to land. And then aggressively bring your legs together a little earlier to do the round off later.