I have never been to Gen Con and don't know much about the parking situation. My hotel is definitely a drive away. I thought about using Uber/Lyft, but I want to be able to take purchases back to my vehicle. There doesn't seem to be any Gate Ten parking tickets left. Will the parking at Lucas stadium be available?
I am not opposed to a bit of walking.

You  can try Lucas oil, but if thats full go out aways past the circle you might find parking that direction. 

The garage across from the convention center is government employee thurs and fri, you can park there on sat and sun.
The garage under the museum is members only this weekend, as well as the lot across from the baseball field.
Sun garage fills up fast by the Circle city mall. 

I would look at a map before leaving and get familiar with the roads and try north past the circle in the center of the city.