Careful not to go overboard with the thread tape, too much and you may crack the valve / pipe.
Irrigation wire is sold by the foot at home depot / lowes, something like this (link).
These are available in the electrical department, just ask an associate to cut some for you (tell them you need 3 or 4 conduit irrigation wire, ~15ft).
I recommend you run separate wire to the relay (you need 2 conductors or more) and the valves (you’d need 3 conductors or more). The wire I’ve linked to has 4 conductors,