How many votes are you allowed and can you get more?
I’m not sure if it’s the same for everyone, but you can see how many you are allowed by adding your present votes to your votes remaining. To see your present votes, go the Feature Requests, My Votes:
To see your vote balance, go to any feature request and hover over the Vote/Voted button.
You can free up votes by “un-voting”. Go to a feature request that you no longer want to vote for and click on the Voted button.
I have no idea if you can get more . . .
The allowed votes are based on your community ‘Trust Level’ which is determined by your activity in the community.
One of the principles that the Discourse team mentioned with the voting plugin is having a limited number of votes to drive prioritization of where votes are cast. As @Bry mentioned, you can always unvote for something if you want to move the vote over to something more important to you.
Additionally, whenever a feature request is closed, those votes are returned to you.
You can also see it in the Activity section of your community profile: