Unless the fuel is being produced on the Moon, it would be more efficient for Mars-bound spaceships to fuel up in LEO. All Earth-departing mass has to pass through LEO, so it's simpler to rendezvous there rather than enter, and then leave, Lunar orbit.

If launches are cheap, then refueling in LEO makes a lot of sense. Historically, this has not been the case at all, but it's all part of SpaceX's model for Starship.