Depends what flavour you want and dishes you make. There is a lot of soy sauce and a lot of dishes made with it. General rule, use cheap soy sauce for frying/sauteing. In this case the acidity is cooked out and it will add a salty umami flavour, without much sour taste. We don't use expensive soy sauce here because like the acidity, the complex flavours only found in expensive soy sauce are cooked off and evaporate into the air.

When finishing a dish or making a dipping sauce is where quality soy sauce shines.

I personally use Tsuru Bishio as it is one of the last, if not the last soy sauce brand to be traditional fermented instead of machine processed. It's important because the traditional method (especially the wood barrels) adds a lot of depth to it. It might be hard to notice it at first but after using it for a while I can never go back. Plus it's a great value since it's so concentrated and strong you need very little of it. I go through a 40$ bottle in about 4-5 months with frequent use.

A sushi dipping sauce I like to make is

2 parts soy sauce 1 part sake A few drops extra virgin sesame oil A small amount of minced shallots 5-6 paper thin slices of raw garlic

It's very strong and a little pungent (meaning a tingling/burning sensation on the tongue, similar to spicy) but very flavourful. It can be tamed by reducing sake, garlic and adding a few extra drops of oil.

Other than dipping sauces finishing soy sauce can be drizzled over a dish ready to be served/eaten.

Soy sauce definitions

Light soy sauce (usually Chinese): it's thinner than most and has more salt added to it. It's not low quality, simply a different type for different flavours

Dark soy sauce (usually Chinese): harbors a much stronger soy flavour and is much darker (duh!). It has slightly less sodium compared to light.

Finishing soy sauce (usually Japanese): typically much richer and slightly thicker soy sauce with deep and complex, delicate flavours that are easily cooked off accidentally.

There are even more but these are the only ones I use in lots of Asian cooking. I also generally avoid food products imported from China because of their dubious regulation, corruption and pollution that make them potentially harmful. Look for brewed in Japan/USA