]I would say NO, but its not to leave slots open for future melding, you need to cap the Gather/Perception stats if you want to be able to gather all items. But I would use III and IVs in all the guaranteed slots so you not wasting so much materia. But I SB for all my materia and I much rather farm for a couple of IVs, than SB 40+ items for each 3rd and 4th overmeld to get enough Is and IIs.
Also for the head piece you only need 1 gather materia melded to it. since once you collect enough HQ gather tokens you will be getting an upgrade, so no point wasting materia over melding it.
Would keep 606 GP as you goal, not 600GP most suggest so you can use cheapest vender food and not waste HQ better food for getting to 650GP for unspoiled spots. Wouldn't suggest capping it either, since anything over that, is not used since you can't get enough GP fully capped to use another skill.