Generally, a student and their instructor do not wear parachutes unless you will be doing aerobatics. If you advance to flying a single place sailplane, a parachute should be worn. Some sailplanes minimum operating equipment mandate a parachute.

Do not buy a used parachute until you pay for an inspection and repack by a certified rigger. This way you will have a professional opinion of the 'chute's condition.

In any measure, it is better to wear one and not need it than to need one and not have.