Tick anything you already have, in any order. Quests unlock once this is done.
This is not optional and not self-taught. No shop will fill a tank or take you out without certification, and the course includes all the expensive gear.
Find a dive school2 things left above. Quests are real things you go and do, so they only make sense once you have what you need.
First one waiting: Breathe underwater for the first time on a try dive