Is there a guide out there on the best way to make prot? I feel like I overspent the last time I did it.

I think last time, I just did a bunch of low level enchants and combined them until I had a bunch of protIV ub3 books which I then applied to the vanilla armor using an anvil.

Wouldn't enchanting and then combining a bunch of books lower the amount of total possible repairs?

About how much XP should I expect to use for each set of prot? I'm sure I'll end up with a bunch of other enchants too, but we'll consider those a positive externality and still calculate them into the price since I have to do them to cycle the table.

What are the best enchants to put on prot?

I usually add respIII and featherfallingIV for obvious reasons. Thorns lower durability by my understanding, so most people leave them off.

I usually enchant projectile prot for peacetimes because I take more damage from the damn skelly archers than I've ever taken from players.