Most masters start from a few classic combinations. Mint goes with almost everything: with fruit it adds freshness, with berries it gives a cool sweetness.
Citrus and berry, like lemon with raspberry or orange with blueberry, is a safe choice for a group, because few people dislike it. For something softer, try peach or apricot with a little vanilla.
Ask the master about house mixes, since every lounge has its own. Describing what you like (sweet or sour, fresh or creamy) works better than picking flavour names from a menu.