Don't just chuck bubbles onto people for no reason. Don't engage a fight with your bubble active, you'll lose it before the fight starts. Supports are your best bubble candidates, they're usually being targeted, stick by them and bubble them if trouble comes up. Bubble teammates diving in like Genji, Winston, etc. Coordinate with your healers and your dps divers and you'll always have a good amount of charge. Bubble when you take damage not to prevent it