I speak as a PhD in Pure Math, as a director of two companies, one of which employs programmers, and as a coder who writes stuff for myself, and for others.

None of the stuff you mention is essential for a startup. It's likely that almost none of it will be the vaguest bit relevant to your startup before you have to be employing people. If your "startup" fails, or turns into a small side-line, then almost nothing of math or algorithms will be essential.

However, if your startup really does go "viral" and take off in a big way, only then will scaling matter, and at that point the math and algorithms might matter.

Until then, the only math you need is: "How will I make money from this?"