I purchased the Sanctus Material add on (Click on this link to buy) from Blender market and think that the materials he has are quite Good. Certainly saved me lot of time if I had to make these materials myself and I think I would be hard pressed to make materials as well as he does.
I am by no means a blender guru but I found using these materials Made my objects look better.
Blender is a powerful program and if you don't have a fast enough rig, you won't be able to do the things you really want to. Forget about simulations, or large scenes.
Get 32gigs of ram or more, (ddr5 ram just dropped in price), Get a VideoCard with 12gb of vram or more, get a large M.2 drive, and an 8 to 16core Processor.