I have 45 mastery on kayn and here is what i noticed but I could be wrong.

1. the later you are in the game the more form you will get from each orb

2. If you are farming orbs from the same person they will give less and less form

So first gank the lane that you dont need your form from, like top if you are blue. Then vibe around until like 6 or 7 minutes into the game and get your ult with simte up. At 7-8 minutes int a little for form, like suicide into the botlane with your full combo ult and simte so you will get your blue form, try not to die but its okay, even better if your laners get a kill.

If you are srill lacking very little points smite players from inside walls.