Beginner

 A good description of all the Compositing nodes

This person is able to explain and show how to use the cryptomatte in a very clear way.

How to do greenscreen in only a few minutes tutorial. Using masks, and keying out the green color.

 Martin shows you a complete workflow of how to composite images in blender using image planes with transparency.  I think this is useful if you have less ram than you should in your computer.  If you have enough ram, and For more control, watch the cryptomatte tutorials below.  A good practice is using the frame feature to label the node areas, which he does to make your nodes structures more understandable. I would say you might even want to add frames before you start as a way to plan your composite, adding frames and later filling them in with nodes.  He shows how to render your composites to folders as png images because rendering to an mpeg although easier means the output is compressed and loses quality, not good if you have to use the animation later.  Better to have the high res uncompressed stills available.  One tip I liked was how he moved the composite view above his node trees which made working with the nodes I think easier. (blender default is the view is centered)

Intermediate

Using Cryptomatte for compositing. (uses cycles) The ultimate Render pass.

A good reason to use render passes,  My brother has worked on several animated shows and films and used RenderPasses in Lightwave for years and Used Digital Fusion for the Compositing.  Blender has 3d and Compositing in one program.  Render passes are easy to use in Blender, Dylan goes over what Passes to use and why.  Very informative.

He talks about how and why to use Render Passes

He talks about some of the updated features of how to do greenscreen in blender 2.8

Advanced

Ian shows whats possible with Motion Tracking, compositing, and 3d elements. Inspirational.  The sci fi train, and sci fi elements define the mood of the scene. 

His explanation is straight forward, but the conepts and ideas are advanced.

More of his lazy tuts which are quick ways to make useful things like flags and banners waving.  Super quick to make.

He makes a very realistic scene and uses an actor with green screen.  He uses Mega scans which I think help make his work really shine.  (Subscription if used in blender, free in Unreal)
He talks about how he created the scene, and some of the node setup for the textures. (He shows how to make a wood texture)  He doesn't show how he has the green screen directly in blender but that's possible using the compositor