Cinnamon: Wonderfully aromatic and rich, cinnamon is enjoyed in a variety of Chinese recipes, and in particular braised dishes. It's also a crucial ingredient in five-spice powder. Chinese recipes often call for cinnamon sticks or bark; be sure to remove them before serving.
Hot Mustard: The sharp, horseradish-like taste of dry mustard can be used to add kick to sauces and marinades, relishes and condiments. It works well with other strong spices. Brown mustard seed is hotter than yellow. Toasting the seed brings out a nutty (rather than hot) flavor.
Cilantro: A staple ingredient in southern China, this pungent, fragrant seasoning is the leaf of the coriander plant. It's also called Chinese parsley, and it's similarly used to garnish as well as flavor foods. While the flavor is pungent, it dissipates a bit with cooking.
Curry Powder: Chinese curries tend to be a bit milder than Indian curries. Use a ready-made blend for convenience, or develop your own mix of spices (like chilies, cumin, ginger, celery seed, pepper, cloves, caraway, turmeric, paprika, fenugreek, garlic, mace, and/or lemon peel) to customize your dish.
Orange Peel: Fresh citrus peel (orange and tangerine) is found in Chinese markets; dried can be used to add the same fresh zest to recipes. To use, rehydrate the peel in warm water for about 20 minutes.
Garlic: Chinese cooks use garlic to flavor oils and sauces, and you'll find it in most any stir-fry. Garlic works well when paired with another strong ingredient, like scallions, ginger, or curry. Garlic flakes, powder, and granules offer convenience.
Salt: Much of the saltiness of Chinese recipes comes from the liberal use of soy sauce, but Chinese cooks also use sea salt, which is found in many Chinese markets. The minerals in the salt (which are taken out of common table salt) are thought to contribute to the flavor of the salt.
Onions: Like garlic and scallions, onions are used in a wide variety of Chinese dishes, and stir-fries in particular. Onion flakes, powder, and granules are convenient ways to stock up.
By the way, while you'll find MSG (monosodium glutamate or wei-ching) in a number of Chinese recipes, good spices make the crystalline chemical--used to enhance flavors--unnecessary.