2nd batt is a plus, ho alt is a good idea also, definitely do the big 3 first, as far as hardware for the back batt you need 3 fuses( 1 within 12" of front batt,1 within 12" of back batt and 1 between back batt and amp), 1 run of 0 gauge from your positive post on your front batt or you can run 1 from your charging post on the alt, 1 0 gauge ground from back batt to good ground(frame,shock tower bolt,ext)and away to hold the batt down(tray,box)you dont want it rolling around back there