Character Advancement
From Unusual Haunts
Characters don't advance by gaining extra activities (there's no more time in the week!), but they can improve in other ways.
Activity Improvement
Investing resources found over the Bridge in to the activity of your choice can improve what it teaches. This will be a slow and gradual process though.
Poisons
It's known that more exotic ingredients fed to a Poison will cause it to have more powerful effects. Those that attend Evan Jones' workshop can particularly benefit from this.
Rites
Rites are mixed bags, allowing you to "sharpen" your ghost. This usually seems to come with Consequences.
Haruspicy
The backing of a good ancestor can give you extra abilities. If you can reshape your family tree via Haruspicy to fit them in.