As derived from the wiki:

On the surface, Dandy seems to be a kind, responsible and bright Toon, but also suspicious and harboring darker secrets.

Dandy seems to either be impatient or scared of being ignored. Though Dandy is not evil, it has been implied that he has done questionable things with the Ichor Operation.

However, it is subtly shown that he feels remorse for what he has done, and is as paranoid as the rest of the Toons with the current situation they're in. He also subtly shows that he fears losing his friendship with the other Toons. Yet, he tries to cover most of it up by acting cheerful in most regards.

Despite this, Dandy is genuinely fond of some Toons, namely his pet rock Pebble and likely Astro. It's been implied Dandy wouldn't be a bad owner to Pebble and that Dandy and Astro's relationship is not toxic. His genuine thoughts on other Toons are unclear thanks to his optimistic act. Overall, Dandy is relatively morally gray.

His voice should be masculine and young, and silly sounding like the lead in an old fashioned cartoon (duh)- but his voice actor should also be able to shift their tone into a more threatening one when needed.