it depends on the potion you plan on making. you can use urine for a binding or protection [i've heard both] to make it really strong, a woman's urine while she's menstruating.
i heard of an old korean potion [which i wouldn't do] where you take a piece of rock [best if it's from a holy statue] and grind it into powder, mix it with water and drink it. it's a type of fertility potion. old wives tale if you ask me, but it's neat to know.