How to play Morgana Support?

I'm new (lv 13) after trying a few heros I really like Morgana. Been trying bottom lane support (against intermediate bots). From my understandings these are the priorities:

1. Dark Bind/Tormented soil enemies that the ADC can finish off
2. Shield ADC when they are attacked
3. Push wave forward with Tormented Soil
4. Try not to get last hits when ADC is there last hitting.

But what do I do when ADC runs off? follow? hold the lane? Sometimes I can't really stay close to the ADC b/c they are going in and out of the jungle, or they are aggressive and chase past the tower. Should the rule of thumb be where ever ADC is I am? Even if they leave the lane?

When ADC teleports back, should I do the same or use that time to farm extra gold then teleport? Negative of that is I will be alone, and ADC will be alone for a while as we are off sync.

Also I'm not great with her ult, so if you also have tips on when/how best to use that, I'm all ears.

Thanks