I would say Shadow Ball is a must to hit all of the Pokemon and get STAB. In Gen 3 Shadow Ball is a physical move which works out very well with Sableye's higher attack stat. As it's a Double battle you can also go for Fake Out which will help you gain an upper hand on the first turn.
Really the other tow moves are whatever you want because all you need is Shadow Ball which will hit all of the Pokemon for Super Effective damage.
Shadow Ball and Fake Out are the two moves I suggest you definitely have, then whatever else you want.
