
Most used spices by me - most of what I cook are kinda stew-like curries similar to the Indian food available at restaurants nearby. India's a very, very big place with an amazing diversity of cuisine, so no short list can be accurate, and doubt any one person could put together a semi-comprehensive list:
Spices:
* black mustard seed
* cumin
* coriander
* cardamom (definitely green, but black, too)
* cloves
Herbs:
* bay leaves
* curry leaves
* fenugreek leaves/methi
Aromatics:
* garlic
* onion
* ginger
Peppers:
* spicy green chilies (I use serrano, but that's what is easy to find and mild enough for the rest of my family)
* Kashmiri red chili powder (pretty mild stuff)
Fats:
* canola oil
* ghee
* mustard oil
Also, tomatoes, curd/yogurt, and coconut milk.