I make most of mine with a piece of sheet lead below the leader hole and fix the shell, reflective tape etc to the sides of the lead. But everyone has their own style. I've seen good looking lures made with small plastic boxes or tubes filled with resin, drilled to fit the leader tube and wrapped with reflective tape.
Here are a few of mine:
I've had good results with lure heads that were just solid black or white. Getting the lure made right (centered leader tube, weight etc) is the most vital step if you are just starting. Good to hear about those blue fin tuna catches, they seem to take lures real well down your way. Bet you can't wait to land your first "barrel" on one of your own lures.