If you have AP or transfer credit for MATH-221 (Calc I), take MATH-222 (Calc II) or ECON-505. While it is possible to avoid Calc II or ECON-505 by taking both ACCT-240 and CSC-280, it’s not a wise course of action.
Calculus is not required for ECON-300 or ECON-301, but it is helpful. Calculus is required for ECON-500 and 501. If you take ECON-500 and 501, you may take 5xx elective courses. Advanced undergraduates who performed well in ECON-300 and 301 may petition the instructor for admittance into a 5xx elective.
Your life will be easier (and your grades will likely be better) if you take STAT-202 and ECON-322 in back-to-back semesters.
What if you decide on the BS in Economics a little late and this plan won’t work exactly? Take the economic theory sequence (Calculus-ECON-300/500-ECON-301/501) in as quickly as possible. Concurrently, take the tools sequence of Statistics-ECON-322-ECON-480. Get these courses in ASAP. Fit in ACCT-240 or CSC-280 whenever you can; sequence is not important for these courses.
Note that ECON-480 (Senior Research Seminar) is usually offered only in the fall; independent study to replace it is strongly discouraged. It is fine to take field courses at the same time, and after, ECON-480.
The complete list of requirements for the BS is here.