Preface:

This is just my experience with material trading.  I’ve filled my entire materials storage to full twice, and while it is a soul-sucking and time intensive process, it does result in having some super fast, strong, or long jumping ships and worth every second of the grind.

First off, I followed a lot of advice from this youtube: https://www.youtube.com/watch?v=iHl-SsKQfe4, and additionally from https://www.youtube.com/watch?v=-4HClk1cRIo

There is a lot of logging off and back on, and even crashing to death to save time involved, so you should be ready to invest not only time, but credits.

Now onto the usable text.  These are notes from the above video on material gathering using the log-off and repeat method:

The first video mentions using the map to find sectors in certain states, and using your scanner to look for the high grade emissions.  For the below breakdown, use EDDB to find the correct “Faction State” nearest your “Reference System”

Material: Allegiance – State – Population
Core Dynamic Composites & Proprietary Composites: Federation – None – High Pop
Imperial Shielding: Empire – None / Election (Also found in Outbreak) – High Pop (GRIND THESE)
Proto Heat Radiators and Proto Light Alloys: Independant – Boom – High Pop
#Could not Spawn# Military Grade Alloys: Any – War / Civil War – High Pop (Less Common)
#Could not Spawn# Pharmaceutical Isolators: Any – Outbreak – Any Pop (Hard to Spawn)
#Could not Spawn# Improvised Components: Independant – Civil Unrest – Any Pop (Also spawns Proprietary Components)

I noted the ones from the video I had trouble with, I welcome you to try and see if you get better results.

This will gain you a lot of materials, but not all of them, you will have to constantly trade down to fill up the G1-G4 materials.  Trading across to other types is costly, avoid if possible.

And then for some more materials that you can grind without limpets, you can also do Robigo Runs (explaination of a Robigo runs: https://www.reddit.com/r/EliteDangerous/comments/8yp8jm/robigos_back_how_to_make_120mhr_easy_low_barrier/), this will allow you to get even more materials, so you don’t have to waste the exchange rates at the material traders.  You will want a long range Python to do this in only 2 jumps to make it as fast as possible, its a good first ship to engineer for as well.

The most important thing I can say is, be careful when trading.  Not only is the interface confusing, bus you can lose hours of work if you trade from a smaller material upwards.  Always try to get the g5 materials directly, it will always take less time.  Trade g5 to g5, it still will lose a lot of value in trade, but not as bad as going g4 to g5.