Charisma is gained randomly from the following actions/events

1. Complete school courses
2. Riding Murfin Madness
3. Decapitating Fairy
4. Puchalla Inn quest
5. Completing Level 13 of any of the 3 Simerian Temples (gives you 5 Charisma Stats)

Links
www.marapets.com
www.marapets.com
www.marapets.com
www.marapets.com