yeah!!
previous FF's weapon were always in the need whenever u arrived at a new town.. i.e buying a weapon will increase u'r STR, armor will increase u'r DEF, etc

FFX, though, is different. You need to concentrate on u'r sphere grid rather than u'r weapon. Just like what Shoden said, I only used Brotherhood (or other weapon only when the fiend is water-based) and Caladbold for Tidus. Sure there are certain times when the weapon gave out Str +3% or 5%, but the main thing here is to stock up u'r items, so that u can customize u'r weapons and armors later on.

To me you don't have to buy weapons too much, and level up whenever you're near a save sphere, so that you can stock up your gil and strenghten up your character.

Does my explaination helps?