Outside of those spells, I also learned the OWL level Silencing Charm, which I feel is entirely underrated. Getting this off against anyone who isn’t a NEWT level student is effectively an instant win, especially since I can use the same blood casting method to make THIS one reapply itself after it’s dispelled so long as I kept feeding it magic. Following that spell is a few other dueling essentials, such as the Shield Charm, and the Stunning Charm. Stupefy might be a bit cliche, but cliches work.