Math 53 and 54 can be taken in either order. Math 54 is required for L&S CS while Math 53 is not.
http://cs10.org can give you a preview of CS 10. http://cs61a.org can give you a preview of CS 61A.
Assuming that you have AP calculus credit for Math 1A, you may want to try the old Math 1A final exams to check your knowledge:
https://math.berkeley.edu/courses/archives/exams
https://wim.math.berkeley.edu/past-exams/
https://tbp.berkeley.edu/courses/math/1A/