Preparing a strong Biostatistics PhD application

[rickck]

I am an MS student in CS (and Math/CS undergrad) with the intention of applying to biostatistics phd programs. 

Background: I have taken the required background courses in mathematics for biostatistics phd programs (probability, linear, advanced calculus) among several other math courses (not related to probability/analysis/stat) coming out with good grades, and have some biostatistics research experience but no publications yet. Will be taking mathematical statistics and a graduate probability topics course.

In preparing a strong application for biostatistics phd programs, what advice in general do you have?

should I focus on research experience and publications? should I focus on taking more advanced mathematics courses (like functional analysis)?

Since my MS is accelerated, taking the advanced math courses while dedicating a lot of time into research is not very feasible for me.