Hey there,
Full time British voice actor here, I can take you through what we usually appreciate from a game dev when being contacted about collaboration...
A little intro about who you are, links to your company profile and previous/current work.
Details about the production and the character you would like the actor to play. If an accent or specific age range is required, let them know! Include a rough word count.
If you have a strict budget for what you can offer for the role, be upfront about this from the get-go. Many voice actors negotiate their budget for each production, based on what is being asked of them. So, there's often a middle ground that you can shoot for, even on a limited budget.
Where will the game be released? When are you expecting to record, and is this a one off gig or a role that may grow in the future as the game develops.
Once you've mentioned these things to a voice actor, they'll be able to get back to you on if they are interested and available to provide the work you've asked for.
Drop me a line if I answer any more of your questions.
Kat