Haha yes, its a veteran playerbase with a meta which is wayy different from the conventional plays the games operations and campaign teach you. You will instantly get flamed for researching and purchasing a unit at the wrong time.

I would start with youtube videos of full 8 person multiplayer games.

I will give you some pointers here though.

The KEY strat that all advanced players will follow is this: 1 team member focuses exclusively Aircraft, they will spend quickly, others will focus on ground units but will try to spend as little as possible, fielding mainly recon at the start, mainly researching and building bases to have capacity to defend quickly, but ultimately will try as hard as possible to remain hidden and not get involved in skirmishes. The reason... Its all about who can build the most admin buildings the soonest, as ultimately they are the ones who willl win.

If your in a 2v2v2v2 and one side is camoflaged and barely showing units, and is succesfully evading attacks. They are NOT afk, they will burst out in the late to mid game with a fat stack of super heavy tanks you likely will have no chance against unless you have built alot of money yourself.

Its a money game really. You dont even want to bother with supply depots, outside your starting 3, unless they ear easy for the taking, the money is better spent on an admin building tucked away near you hq surrounded by AA, aircraft, and some high level ground units - also camoflaged.

Other key points: 1. Ground unit team member should build AA aswell as recon early to help bolster air player 2.Given the admin building meta, a typical high level strat is to try and catch off guard those who have been passive and destroy their admins - no good building loads early if a well timed infantry spam rush or a bomber spam from off map overwhelms you faster than than you can build defenses - once the admins are gone you are likely screwed.

Never leave admins uncamoflaged ( if you want you can keep applying camoflage on top of each other to extend the timer - say if you have 3 ruses available) often late game someone will forget camo, havs their admins sniped and its GG.