2. Also, the main weapon affects the burst damage of your soul by changing the multiplier. That's why for main weapon, try to get your hand on the highest rarity weapon that is a) equip-able by your soul and b) compatible with your team's overall element.

3. All weapon skills apply, be it main or sub, BUT only to the himes and soul that match the weapons' respective elements.

4. You can see the respective Gacha contents, as well as the % odds, near the bottom right of each screen.

5. If by potions you mean those that replenish your HP in battle, then no. They only drop from mobs and they don't roll over to your subsequent battles. However, Elixirs purchased by $$$ or jewels give you a full heal, but it is less recommended to use them simply to heal. Side note: that's why healer himes and souls are good.

6. Gauge restriction only matters once you stack the master bonus to higher amounts (i.e. unlock Siegfried etc). It is there such that you can fill/deplete a rage-bar equipped boss as you wish. Doing so may enable some special effect skills to work better (such as increasing damage only when boss is raging, or increasing damage when boss is stunned)

7. It's totally fine to not spend $$ on this game. In fact most people don't. So the best option is to go for Disaster Raid SR attack weapons and limit break them. As for limit break, it is there to break the level cap of your weapon/eidolon/hime. Limit breaking does nothing to the stat otherwise, except giving you a higher ceiling towards the max level/damage for that particular item in regard to leveling up.

Also, no question is stupid. We're happy to answer them.