Using my recipie book idea you could create books for play styles. Players could get only recipe books that help their style or invest in all the books. It would also allow for easy addition of curses later on.
Example - book 1 has 5 spells and comes with the hut, or in my example the kitchen
For aditional spells you need to purchase and read books
I suggest spell books include 3 ultra rare and 2 legendary curses or something like that where there are basic and complex recipes.
This would be part of the hut called a library. Books take money and research time to acquire.
Book 2 mecantile curses - 5 curses
Book 3 pirate curses - 5 curses
Book 4 nobility curses - 5 curses
Book 5 advanced legendary curses - 5 ultra complex curses for witch doctors.
Book 6 general curses vol 2 -5 curses
Books could be added as more curses are established.