My first stretch goal is about $1750 in order to increase the gameplay by nearly one or two more hours per route. The production of sprites and music can be costly, but it's needed to keep additional content from being stale or becoming filler. Therefore it can be more difficult to increase the content.
This first stretch goal would likely entail:
- Additional gameplay and story branching
- More CGs and character outfits
- Holiday themed CGs and outfits
- Additional side-character development
- Possibly additional main characters
Beyond that goal, I would likely use the money to try publishing on mobile platforms, and then for additional content delivered on holidays.