I am by no means an experienced competitive player, but here's a set.
Weird introduction anyways
<----- LEGS :OO
Legs (Tsareena) @ Life Orb
Ability: Queenly Majesty
EVs: 252 Atk / 252 Spe /4 SpD
- Trop Kick
- High Jump Kick
- Play Rough
About the set -- with a mediocre Speed stat, sitting at 72, it'll have a fantastic time being outsped by a ton of stuff. No Scarf, though, because Synthesis, High Jump Kick and Life Orb works really well. It has surprisingly okay defenses, at 98 both. Because of its mediocre speed stat, it had to be fully invested. Alternatively, you could probably run Scarf and an Adamant Nature, and replace Synthesis with U-turn, as you'd probably not pit it against other Scarfed Pokemon. Queenly Majesty is its best ability, the way I see it, even though it'll get outsped anyways, switching into a predicted priority move could be a good way to get her in untouched.
Then, the moves. It's meant to be an all-out attack set, with moves designed to decimate the enemy team. Trop Kick is her only good physical STAB move, plus the added bonus of lowering the opponent's attack. Synthesis is general recovery when you find the chance, to give her longevity and just in case of High Jump Kick missing and Life Orb recoil. High Jump Kick is just super powerful and random coverage, and Play Rough is the same.
An alternative set is a Choice Scarf set, same everything except Scarf item and U-turn instead of Synthesis. I've never really enjoyed using Choice sets as well, but it could help get her Speed up, which is her biggest downside by far.