Yeah, I agree with CloudyMagpie, that honestly sounds like plenty and pretty rad.
Okay, so in your concept, everyone in the world has one of these crystalised dragon souls. So they live in a world where that's normal. The Dragoons are seven people who are uniquely powerful, so there are a few ways that could happen:
They just got really good at using their dragon souls. They're like the special forces badasses of their world who through a mixture of natural aptitude and intense training (perhaps in an academy or under masters) have become incredibly awesome at specifically using their Dragon Souls for fighting. Maybe there was some big trial or contest, or they were hand-picked by a master or the last team of Dragoons. Showing why each member was chosen could be interesting.
They had their dragon souls empowered through some sort of ritual or artifact and now theirs are more powerful. Were they chosen for this role for talent? Or did it just happen to them and they need to prove that destiny or the gods made the right choice? Did they go on some kind of dangerous quest or do a feat to acquire it? Showing how each member got empowered could be interesting.
When the dragon souls were handed out, either through deliberate choice or entirely by accident, these folks got extra-powerful dragon king/queen souls. Maybe with some of them it was known this would be the case, like, I dunno, some of them are from ancient bloodlines like royalty, warrior nobility or organised crime who always give it to one of their own when the last bearer dies... but throw in at least one or two who got it in other ways, like... I dunno, the last bearer of a king soul died on an adventure and their crystal got found by some kid, or a king soul crystal got mixed in with a bunch of normal ones.
Because "it gives you armour, but fancier than the basic little bits a normal person can summon, a weapon that's flashier and stronger than the normal basic spears, daggers, hand-axes etc. that normal people can summon, and when combined lets you summon the freaking Megazord" is rad enough on its own. The thing that will make it really interesting is: How they got these special powers and how it makes them feel. What pressures does it put on them? What Dynamics does it introduce to the rest of the group if say, one of them is a Prince or Princess who just inherited power, one of them is a "genius of hard work" who got it by getting the best grades ever at magic school, and one of them is some random peasant who just stumbled onto it? That's where the interest will be.
