Here's my suggestion for containers & soils.
I usually get cheap cactus seeds from dollar store or wherever and use them as test models for growing.
What you can do is make up different soil combinations and containers and plant the seeds in them. Watch to see were you have the best germination. Then use that soil and container for growing your important seeds after removing the test seeds.
So many times I have tried different formula's and containers that were recommended only to find out that I wasted good seeds. I think that different soils have different compositions of bacteria, both good and bad but its not consistent. Only by growing in it can you tell which one will work.
It took me forever to catch on to this simple trick !