For the first time of using C4Ds, it's not bad. Though I'm not really getting a sense of flow here, I think Ventus's face might be a bit too ovesharpened. And I'm not sure if it's there, but if you have a drop shadow on Ventus, I'd say lose that too. I do like the C4Ds you used though, with a bit more practice I think you could make some pretty nice stuff.
Ven's placement seems a little awkward and there's not really any flow. The colours look a little funny together, and don't really mix together.
i thought it was pretty good except that with those colors you could've done something a littl emore creative like making vanitas his shadow and making a name below his upside down that says vanitas. the colors work with him more than with ven. but still not bad for your first time.