Switch to barrier tank!!!11.
Really though, I don’t think there’s a ton of tips to give on Grav. D.Va is out of meta so you don’t have to worry about it getting eaten too much – it’s more just looking to get at least 2-3 enemies AND making sure your team is in position to follow up on it.
The latter is probably the most common mistake – even if you Grav 4+ people it means absolutely nothing if your team can’t immediately follow up on it. They’ll just float for a while then communicate to their team, “Zarya wasted Grav!”.
It’s honestly better to get 1-2 key targets (like healers) with immediate kills then get a big Grav when the team can’t do anything with it.