The main spices one must always have are cumin, corriander, turmeric, red chili and garam masala. In most cases, Indian households have both whole and ground versions of each spice, although turmeric is only found in powder form.
Garam Masala is a special mix of a few Indian spices which is what creates a certain flavor. It literally translates to "hot mixture" and is used in both cooking and as a garnish. It has black & white peppercorns, cloves, bay leaves, black cumin, cumin seeds, cinnamon; black, brown, & green cardamom, nutmeg, star anise and coriander seeds.
Some of these spices like cloves, cardamom, nutmeg, cinnamon, star anise and bay leaves are also necessary in Indian spice cupboards.
Another used concoction is curry powder. However, unlike the mix of curry powder you can find in a grocery store, this isn't just curry leaves ground up.
It is this specific combination:
- 2 tablespoons coriander seeds
- 1 tablespoon cumin seeds
- 1 teaspoon fennel seeds
- 1/2 teaspoon whole cloves
- 1/2 teaspoon mustard seeds
- 1 tablespoon cardamom seeds
- 1 tablespoon whole black peppercorns
- 2 dried red chiles, broken in pieces, seeds discarded
- 1 tablespoon turmeric
As you can see there are many spices used in Indian cooking. The best thing to do is get them in their whole form and blend a small amount to use regularly when cooking. The spices in powder form lose flavor after about 6 months, while whole spices, if left in a cool, dark, dry area can last more than a year.
Have fun with the spices. Try them raw and see what they taste like and how adding them can change the depth of your dish.