Creating a buff that is obtained by interaction/motives?

Since this isn't about S4S we can't help you much with it, and I'd recommend joining Zerbu's discord for further help. You can "count" something by making a commodity. If I were attempting something like this I'd make a loot, inject it into one of the loots of the interaction I want to count, and then in this loot have it increase the commodity by...whatever number you want to say is 1, and then create a state at the max count I want to add the buff in question. So say each use of the interaction is 10, the max count is 100, then at 100 my state triggers the buff. States can be used for your second question as well. Note that MC does not spit out SimDatas for commodities, you will have to manually make one so your states work (someone had this issue just the other day when working with MC and states).