Bear with the noobiness of this question...
 

...But are there figuarts sold of KR: Ryuki? Some of the other Riders are very cool and I'd like to buy some.

Are you asking if there is a Figuarts Ryuki? if so, then the answer is a resounding yes, and a damn good one at that. They also made Knight, Ouja, Blank Form, and others to follow soon.

OUJA!!!!!

Zolda is the next scheduled release for Ryuki Riders. At the moment the only other one revealed is Abyss; the others will probably be made/announced in the future.

Its worth noting however that only Ryuki & Knight come with their Contract Monsters; the other creatures will apparently be sold separately.

They have Ryuki, Winged Knight, Ouja, and soon-to-be-released, Zolda~
The Ryuki line-up was given a lot of love. Well-made.