You're going to get a ton of different suggestions, so the first thing I'll say is that different things work for different people, so pick what you like for each aspect and go with it; it's your game!

I have found the following things work well for me and my group:

Smonex Organizer: https://www.amazon.com/Smonex-Wooden-Organizer-Compatible-Gloomhaven/dp/B084T13QML

Player Dashboards: there are a ton of these on Etsy, all similar but with variations in layout. We love the ones from Zenpy Studios, but look at them all and pick what you like.

Monster Card Holders: Zenpy has the best out there for this, especially because it comes with a modifier deck holder

Monster Stands: look for some kind of monster stand that has a health dial. There are different styles (we again use Zenpy here), but the main point is to not have to track damage on the card holder itself, which is problematic for numerous reasons.

Some of the above assumes analog play -- you'll get recommendations to use an app for the monsters, and if you want to do that, absolutely go for it. My group and I prefer to do it all tabletop except for campaign and character progression tracking, for which we use Gloomhaven Storyline.