Consumables can be handy if you know a big persuasion is coming. I just check how many "points" it takes too convince the npc and don't take any unnecessary risks. I've done a quest line pretty early on that unlock me the manipulation skill early. It gives you an additionnal choice sometimes with safe-ish big points. There's also a skill to unlock the choice to bribe I think. didn't invest in it (i want money!) but it is still a possibility.