Healer here. I've pugged 3 M+ seasons so far
* BFA S3
* SL S1
* DF S1
The first 2 I started playing mid-season, so I had to catch up. It was horrible, took me many weeks to get out of the "bad groups" zone (in SL S1, that was anything at 15 or below), and it was very hard to get invites above that initially. I only got to play consistently in good groups towards the end of the season, but a lot of people had quit the game and there was no cross faction play, so way less groups on the alliance side. Not a great experience.
I started playing DF S1 from the beginning and playing every week. It is night and day. Keeping my M+ rating up from the beginning allowed me to play with much better groups. I like it a lot more this time around.
So my only advice is: grind rating as soon as possible. It's a multiplayer game after all, so being ahead of the curve helps a lot with being matched with similar players. People who are really passionate about this game tend to play more and early. Lots of exception of course, but that's still the overwhelming trend.