Hi David,
In addition to the good advice Bill has offered above, you should be aware there are two online forums that will prove to be resourceful for you based on your location and type of diving.
The first is of course deeperblue which has a tremendous database of freediving knowledge, and the second is
Spearboard which will assist you with its wealth of local La Jolla spearfishing knowledge.
Welcome aboard, start reading, and you're going to like the friendly and helpful environment here!
