Find Familiar + anything requiring a spell attack e.g. Fire Bolt, Ray of Frost and Witch Bolt.
How? Summon an owl as your familiar. It can't attack but it can use the Help action. Order it to fly in, Help and fly out. Its movement away doesn't provoke because it has Flyby. Ready your spell for when your owl Helps and you'll get advantage. Best of all, you can do it every round.
Of course, if a monster uses a ranged attack on your familiar or readies an action of its own to attack your familiar as it approaches, it's pretty likely your familiar will be killed. But few monsters want to expend an action in combat getting rid of something that isn't harming them directly when other opponents are.