Most of the time when playing ap varus it'll be hard to win lane unless you have a braum or a thresh. You want to farm well while stile poking the enemy bot, you want to play for fights for drag or roams because your R is one of the best ultimates in the game. You can easily start teamfights with your R or stop a whole fight by just pressing R. You might get heavily destroyed in the laning phase but you will still be usefull for the whole game by applying cc and heavy constant damage.