[Marileangorifurnimaluim]

I think the rings different in what they were capable of - the three were for preserving, healing, etc., the dwarven rings for great wealth, and the nine for glory and kingly power. The One: dominion. Any could use them, but the rings designed to produce great wealth would especially appeal to dwarves. As for why he didn't make more, good question. He had lost a lot of his power when his lost the One. Perhaps once he recovered it he could have made more.