Board Thread:Questions and Answers/@comment-32844121-20170813033311/@comment-33971231-20170813061417

There's not really a way to increase your chances of getting Larvesta, but the best way to get one is from a Swarm (though it is quite rare for a Larvesta swarm to happen). Otherwise, you should hunt in the grass patch behind Elegant Valley's Pokecenter (where all the Ralts and Oddish are). If you spend an hour straight hunting there I can almost guarantee you'll find it (you can get lucky and find one earlier though!). However, if hunting isn't really your thing I think you should trade for one as I'm sure there are many people with spare Larvesta out there you can negotiate with