Mounted Machine Gun

What are 【Material】 and 【Ingredient】?

These are information of a player. 【Material】 and 【Ingredient】 by themselves do not hold any special abilities, but they may be gained or consumed by card abilities.

With an ability that states "Consume X [resources]," can I choose 0?

Yes, you can.

I have multiple copies of the same card with a [Once Per Turn] ability in my base. Can the [Once Per Turn] ability be activated once for each individual card?

Yes, it can be activated. For example, if you have multiple copies of TD01-008 〈Stone Pit〉 in your base, even if you activate the 【ACT】 ability of 〈Stone Pit〉 A, you can still activate the 【ACT】 ability of 〈Stone Pit〉 B.

I consumed 2 Materials for the 【ACT】 ability of BP01-015 《Mounted Machine Gun》. For "Choose 1 Pal, and deal 500 [Damage]," can I choose the same Pal twice?

Yes, you can choose it. Since you perform 〈Choose 1 Pal, and deal 500 [Damage]〉 twice, you can choose the same Pal twice, or choose different Pals once each.