1. Pre-Haas people generally delay beginning the Econ 100/101 series until their 4th semester so those grades won't affect their GPA for Haas since those classes have a reputation for being difficult.
2. Somewhat counter-intuitively, may people also take Econ 100B before Econ 100A since the former is less math-intensive than the latter, which eases the transition from introductory to intermediate economics.
3. I agree with ucbalumnus; if you are interested in taking Math 53, maybe Math 54, stats classes, etc. you may want to consider a quantitative major or minor, especially as a back-up plan for Haas (perhaps alongside a major in econ).
4. You also have 3 pre-requisites in your freshman spring semester; you may want to be careful in combining more than 2 pre-requisites in any given semester, just as a rule of thumb.
I think the ideal schedule to maximize GPA (assuming you are prioritizing that above a second major or a minor or graduating early) would be to spread out your pre-requisites and to delay the Econ 100 series (which is easier to do well in GPA-wise than the 101 series) until spring of your sophomore year since that is the first semester for which your GPA will not matter for Haas (except for retaining your conditional admission, which is negligible). Also note that Stats 20 and 21 are generally regarded as similar to one another in terms of rigor, so choose which one to take based on which fits better with your schedule for a given semester and the professor.
Maximizing GPA would entail choosing courses that one likes. Obviously, the business prerequisites are mostly specified. Presumably, the student has an alternate major in mind whose prerequisite courses should be at least interesting enough to do well in.
Specifically in terms of the math courses, a math fearing student should just stick with 16A and 16B. A student who likes math and is good at it should not fear 1B, 53, or 54 and may find those courses more interesting. The OP seems to be conflicted -- fearful of 1B, but wanting to take 53.