I recently bought a mushroom kit and was wondering what substrate I can use to increase my production yield. I know I need oak sawdust but the other ingredients are hard to figure out I tried asking the people who sold it to me but they act like I am not smart enough to understand how to culture my own spawn so here I am asking on the site to see if anyone on here knows, I would love to get a fully sustained mushroom garden growing so I don't have to keep ordering kits when they die out

There is a lot more to it than can be explained here in the forum.

See this link:
unapcaem.org/publication/TM-Mushroom a 65 page .pdf

Go to Chapter 3 MUSHROOM CULTIVATION TECHNOLOGY (CONTENTS FOR A MUSHROOM
TRAINING COURSE)
3.1 Major Phases of Mushroom Cultivation
3.1.1 Selection of An Acceptable Mushroom Species/Strains
3.1.2 Secreting a Good Quality of Fruiting Culture
3.1.3 Development of Robust Spawn
3.1.4 Preparation of Selective Substrate/Compost
3.1.5 Care of Mycelial (Spawn) Running
3.1.6 Management of Fruiting/Mushroom Development
3.1.7 Harvesting Mushrooms Carefully

Your main interest would be chapter 3.1.4 Preparation of Selective Substrate/Compost.