Depends. Depends on the condition of the gelcoat. If it is lightly oxidised use the cleaner wax followed by the Flagship wax in the black bottle.
Flagship will not remove oxidation or other stains & dirt. It is a pure wax & will outlast any multi purpose cleaner wax.
For me Flagship is a once a year application on the sides & rear cap. 9 years & still looking real good. Been using Flagship on my saltwater kept boats for many years.
The trick is using the proper product for the job. A multipurpose cleaner wax will give a satisfying result but it won't last long. A pure wax might smudge stains & marks around but it won't remove them like a cleaner wax will.