Mitsuwa is my go to place for sashimi grade fish.
Sahimi grade must be treated as such from the catch to the table. It is not enough to just look at a fish and say, I will sell or serve it as sashimi garde because it loooks good.
I have had good luck with the tuna sold as sashimi grade by Fresh Farms.
As to shoyu, the best are the Japanese artizen made aged in cedar vats sold at Mitsuwa but be prepared for a price shock.
Condiments, palate cleansers are gari(ginger) and shiso leaf which i am particularly partial to.
Yuzu rind for hirame, clam, shrimp and wasabi ranging from fresh(Mitsuwa) to a range of prepared styles and powder. Mitsuwa includes a small pack of prepared wasabi with fish that is kept refrigerated and is quite good. All but the fresh root probably has horseradish as the main or an additive ingrediants.
You must have short grained rice grown and sold for sushi. Apprentices spend years learning how to make sushi rice.
You will have to develop your own method which will include variation for your climate, water, rice and method.
Your local library may have books on preperation. There are many on the market but simple and pictures to start with are best.
A sharp and I mean sharp knife is essential for clean cuts, rolls and other preperations.
Watching a classically trained sushi chef is also a good idea. Kuni and Katsu come to mind.
I would start with sashimi, then chirashi(scattered sushi), rolls, temaki are fairly easy and blocks before nigiri sushi.
Cleanliness is very important.
Good luck.-Dick