Algebra is usually the starting point, then usually simple geometry then trigonometry, but in my opinion, u can go directly from algebra to trigonometry to calculus without really much geometry. I Wouldn't worry too much about different base number systems. In my opinion, math is pretty interconnected, think of different branch of mathematics as using different approaches and tools to study mathematics. But just do this Algebra --> Geometry --> Trig --> Calculus, that is the typical high school route in the us and it seems to work good for the kids who put some effort into learning them.