Mathematics is the backbone of a data scientist. To become refined in this domain probability, combinations, permutation, a simple understanding of database and strong command in data structure is must. Chain rule, local maxima, minima, hessian matrix, slope of tangent are some core areas whose adequate knowledge is needed for model building. Along with this one must have strong hands in object-oriented programming concepts.
Here are some useful resources to help you better. For essential mathematics to build concept please practice below codes from my GitHub
Essential Mathematics in Data Science
For getting hands on knowledge on machine learning, please practice codes at the below GitHub link
For looking into graphs and Big O Notation which is the foundation for data structure please do have a look at the below link