-용 is a suffix that adds the meaning "for use as/for use during/etc". It comes from the 한자 "用" which means "to use". Naver dictionary page: http://m.endic.naver.com/krenEntry.nhn?entryId=031c9edbd7984109b389d2dbe18ea070&sLn=kr e.g. 식용 - the 한자 for this 식 (食) means "to eat" or "food". So 식용 means for "used as something to eat" or "edible". So 선물용 is something which is used as or can be used as a gift. 선물용으로 would be "as a gift". I'm not native either so I can't tell you the exact difference in feeling between 지인 and 친구. If there is a difference, I would guess that 친구 is a closer relationship than 지인. If that is the case then I guess 지인선물용 would be something which makes a good gift for acquaintances. Otherwise it could just be an expression meaning it's good as a gift for any friend.