First, you need to get far enough into the game to have unlocked the scenario customizer. This will not take too long.

After that, create a game with the following parameters:

Crew: 5
Gnosia: 1
Engineer: NO
Doctor: YES
Guardian Angel: NO
Guard Duty: NO
AC Follower: NO
Bug: YES
Your role: Bug

Your game should look like the image below.



Now all you need to do is play entirely passively. Cozy up to the doctor and if the Gnosia is voted out the first day, you win immediately. If not, just gang up on whoever the remaining characters are doubting on the most and you'll finish in 2 days max.

You should get enough exp for multiple stat increases each time you do this, and the exp scales with your level so this method remains viable throughout the entire game.