Calculus, at its most basic level, requires only a few concepts, most importantly **functions**. You should also know high-school algebra, things like $(a+b)^2=a^2+2ab+b^2$ and similar should be engraved in your memory.
Exponentials and logarithms are one of the fundamental functions of basic calculus, it is thus very important to grasp these concepts.
Complex numbers, although very elegant, and I personally recommend learning them, are not needed for basic calculus. More elaborate topics make plenty of uses of complex numbers, but it is not so hard to learn the most important facts.
If you want some recommendations on where to start learning, the calculus video series on YóuTube by 3Blue1Brown is a _very_ nice intro, and if you prefer a book, _The Calculus Lifesaver_ by Princeton University Press is also very good.