As a start, I suggest learning the following:

Statistics:

\- probability (distributions, basic manipulations)

\- statistical summaries (univariate and bivariate)

\- hypothesis testing / confidence intervals

\- linear regression

Linear Algebra:

\- basic understanding of arranging data in vectors and matrices

\- operators (matrix multiplication, ...)

Calculus:

\- limits

\- basic differentiation and integration (at least of polynomials)

Information Theory (Discrete):

\- entropy, joint entropy, conditional entropy, mutual information