Be a rogue. Get proficiency in whip somehow (feat, 1 level of barbarian, fighter, paladin, ranger, war cleric, tempest cleric or lvl 3 valor bard). Stand behind the fighter/barbarian/paladin. Sneak attack with whip (it has reach!). Most of your damage is sneak attack damage anyway. No -2 for firing into melee like an archer.
Take dual wielding feat and use two whips. Take 2 weapon fighting (if you can) and add your Dex mod to damage. Get to a high enough level in your other class for two attacks. Take Sentinel. If you stand behind the frontline, the enemy won't likely be attacking you ever so you can reliably use the Sentinel reaction attack. That's four attacks. It's easy to get. And you'll almost always hit at least once so you can reliably get your sneak attack damage.
Be a Battlemaster. Take Trip Attack maneuver (and... stuff. you'll never use the other maneuvers). If you knock the target prone, all your other attacks are at advantage. And so are the attacks of everyone else that hasn't gone.
You also don't have to move to do this like you would if you ran up, attacked, and used cunning action. Oh, and another thing, the features I listed above come at all levels so you can start having fun being Devo (Whip it good!) right away.