>>21909755Congrats brah. Pokémon is a very fun game and it's always nice to see new people come into the meta.
>>21909857Make it Jolly with maximum Speed and Attack investment. Knock Off can really disrupt most Pokémon in lower tiers as they are NFE and heavily rely on Eviolite. You might want to replace Heal Bell with either X-Scissor or Leaf Blade. Leavanny isn't exactly bulky, even with defensive investment, so it's better to have a reliable STAB move to use as opposed to expect it to live hits and act as a cleric.
You're probably wondering why I suggested Jolly, that's because Leavanny has a very good Speed tier in low tier games. Also, make sure you use Chlorophyll as Overcoat is mostly useless as it is a Grass type and thus immune to all the popular Powder/Spore moves in Gen 6 (most notable Spore and Stun Spore). Weather is also mostly non-existant in low tier play.