I anneal after every firing. For me, consistency is key and that means doing the same thing to the brass to get it to the same base line- every time.
I started years ago with a drill, socket, and torch. I upgraded to Annealeez when they first came out. Then I upgraded to an Annie induction annealer. That was a HUGE improvement and when I really saw a true discernible difference in my ammo. Since then, I use an AMP. Induction is definitely the way to go, but you need to ensure it's producing sufficient current and won't destroy itself in the process. If you're going to make your own, the GinaErick type is the way to go. There are lots of plans out there if you google it.
Good luck.