“Make the most of” means to use or enjoy something as much as possible, usually because it may not last long. It is a B2 level phrase that you should be able to use in either the speaking or writing papers in the Cambridge B2 First (FCE) exam.
Examiner: “What do you like doing during the weekends?”
Candidate: “I like to make the most of my weekends because I work very long hours during the week…”
Even though the weather wasn’t very good we made the (3)…… of our time there and ended up have a really great weekend.