There's a couple of divers on here that have posted some big fish. I haven't dove in several years now so I'm not your best resource but I can offer some general pointers. First off, before finding good dive spots find out where NOT to go, i.e., MLPAs. Might also recommend joining up with a group like the SD Freedivers, to find like-minded guys and buddies that will join ya. As for gear, here's a basic list:
Wetsuit
Mask/snorkel
Gloves
Speargun and/or 3-prong ("Hawaiian sling")
Fins
Weight belt
Knife
Dive float w/ flag
Tag line, stringers, clips, etc.
Dive light (optional, for night hunts/lobsters)
Fishing license
As for dive spots, those are closely guarded as are hunting spots on land. You might want to start out doing shore dives, kicking out to the inshore reefs and small kelp beds. Then as you get comfy (or bored) with that, maybe invest in a kayak or, if you're a gladiator, swim out to the real kelp beds for some bigger action. Good luck, maybe I'll get back into it and join ya one day.