minimum

From what I understand, the minimum gold cost to purchase a unit (and buildings I think?) is 10. Is this a hard limit though, or is there some way to reduce it further?

Which graphics card is needed to play Civ VI on lowest settings, except strategic view? I am thinking at the ones available at e*** right now, used. I need to buy a new one and want to spend as few as possible, considering the scalped prices.