As for fish sauces, I go for Thai fish sauce and pick. . .
the lightest, clearest colored one I can find in a glass bottle.
Take a look at chin-kiang vinegar (chinese black vinegar). Good for dumpling sauce and sweet and sour dishes (or sour for that matter).
Try to pick up some rice sticks; very nice for pad thai or soups.
As for the oyster sauce, I always buy a brand that has a somewhat chubby woman on it; I cannot remember the name, but it is phillipino, I think. If you can find some try some mushroom "oyster sauce." Pretty tasty.
If you like thai food, try some prepared shrimp or crab paste. Adds a delicious taste to fried rice; everyone loves it in my family, but if you are sensitive to "fishy" you probably should stay away. It is fishy, but tasty. You heat a pan, place a little oil in it, add a couple of spoons full of the paste, stir to break up and then throw in your rice. You can add precooked shrimp, scrambled egg, carrot, onion (green and white), bean sprouts, etc. Serve piping hot and with lime quarters to squeeze over. Good stuff.
Good prepared black soybean pastes are nice to pick up; this is good for flavoring various stir fried veggies like, green beans and broccoli. If you like spice you can look for the hot black bean sauce/paste.