What is a good course load at a reputed undergraduate program in order to prepare well for very strong CS Theory program like UC Berkeley etc
It really depends on the undergrad program. Do well in the relevant/required courses and pick electives that play to your strengths.
@Mathfun11. You could even talk with a graduate admissions advisor and ask them what classes they would recommend. Then all you will need are great grades, strong recommendations, and good GRE scores.
Take some extra math beyond the minimum for an undergrad degree, and get involved in undergraduate research or an honors project if available. It’s not like high school where you have to take all the most rigorous courses across all subjects.