I’m not familiar with what you have access to but here is a recipe that works.
I usually mix soil by the cubic foot(7.5 gallons).
2.5 gallons each part (7.5 total)
1 part peat moss
1 part humus(compost and/or EWC)
1 part aeration
1 cup liming amendment(dolomite lime, oyster shell)
2 cups rock dust (glacial rock dust, azomite)
To this you would then add in your amendments. The easiest way with only getting a couple things is to get an organic dry all purpose and kelp meal. If only using these two, use 1.5 cups all purpose and 1 cup kelp meal. If you find more amendments, just make a mix using equal parts of everything with a double portion of kelp meal and then add 2-3 cups of that mix. Mix it all up and let it sit to cook for a minimum of 2 weeks. Try for 4 weeks if possible, the longer the better.
Other amendments I use or have used in my soils are:
Crab meal (calcium, chitin)
Neem meal (NPK, pest prevention)
Alfalfa meal (N, triacontanol)
Fish bone meal (fast release P)
Bone meal (slow release P)
Blood meal (fast release N)
One supplement I would recommend is some mycorrhizae. These beneficial fungi will help your root system and nutrient availability.
Hope this all makes sense and helps!