Early game:
You need to focus on your Markmans Early game. So your job is to ward tribush, and dragon. And if you're getting ganked from their bushes, ward them aswell. If you don't get ganked so often, 1 ward at dragon ( as Purple ) or Tribush ( as blue ) should be enough.

Early Gameplay:
You should just wait in the bushes, and shield your ADC when he/she goes out to trade, and else just wait around to make plays.

Mid game:
You and your ADC can roam easily. And remeber to remind your ADC to farm, if he/she gets a bit behind. Mid and enemy jungle is a great place to gank ( if you've warded your exit, and gank route ).

Late game:
It's now time where you've got the most of your core build. If your team is hanging around mid. And nothing is really hapening, or you've just won a fight. You can go bot/top. Depending on what's most pushed. With your banner of command and boots enhancement:captain you can lead your minions quickly to the enemies tower, and if you're not getting disturped you might be lucky to get a fast tower. If you do get disturped on the other hand, you should be fine, because of your normal move speed. If the enemy is faster than you. Or you see it needed, you can activate eigther ghost, or your crown. ( If needed both, then use them both )