A friend requested a recipe for a classic miso soup, so here we are.
If you have the time, making your own dashi is effort, but oh-so-worth-it. You can harvest your own Konbu (Giant kelp) and dry it slowly in the oven, otherwise asian food supermarkets should have it. Katsoubushi or Bonito flakes are dry, shaved tuna flakes, difficult to make yourself but again, asian supermarkets will have.
With that said, freeze-dried dashi is actually not bad, and the convenience makes up for the compromise in flavour.
Wakame is a dried brown/green seaweed that is reconstituted in water and eaten as a sea vegetable. You can harvest fresh wakame if you are near the coast, just make sure you are not taking from any polluted areas.