Hello,
I recently got into blender and im taking lessons on it to improve and its going quite well. My instructor gives me the materials to use but when I start making my own things im gonna need other materials.
So yeah, i was wondering where is the best place to get a good variety of materials.
I appreciate any help or answer 
try the BIS
I would take a read on this most all of that theory will translate well to blender (or most any other game engine and such) and while it may not be popular to say but if you understand those fundamentals you can do quite nicely with texturing in blender, blender has quite a few tools that people overlook when it comes to texturing.
I also get a lot of my textures from there, but I make most of my materials using the nodes editor. I like to play around with the nodes and try to create different types of materials, then I save the ones I like for later.
Oh damn, thanks for all that
Or this might be interesting;
EEVEE Shaders on Gumroad.
Because bumpmaps in EEVEE looks pixelated. This package contains 260 seamless normal maps, masks and 35 example shaders. And some tools to design you own materials.