There is no single "correct" sequence of which standardized tests to take or when to take them. Although I can help you decide from a math perspective, there are many other considerations. However, to give you a rough idea, below is a timeline of when tests are offered and frequently taken.
Freshman
None
sophomore
October: PSAT 10, Pre-ACT
junior
October: PSAT/NMSQT, Pre-ACT
November: Nov
December: SAT, ACT
February: ACT
early March: SAT
later March: School Day SAT (required in many public schools)
April: ACT
May: SAT, AP exams
June: SAT, ACT
July: ACT
August: SAT
senior
September: ACT
October: SAT
November: SAT
December: SAT, ACT