If the "gaps" in your Medicare coverage are costing you more than the premiums of a Medicare Supplemental Insurance policy, would cost, then purchasing a Medicare supplemental policy may be a good idea.
If you have group health insurance or private health insurance in addition to Medicare, or you have a Medicare Advantage Plan, you probably don't need to purchase Medicare supplemental insurance.
If you have group health insurance or private health insurance in addition to Medicare, or you have a Medicare Advantage Plan, you probably don't need to purchase Medicare supplemental insurance.