When it comes to Indian cooking, people often get very flustered about having to have a lot of spices. That isn't really true. If you look at a lot of recipes for 'curries', they use 5 basic spices, plus a couple more.
1. Seeds; any one of these seed are used for tempering in hot oil of choice/ghee; cumin/mustard seed/nigella seeds/fenugreek/panchpooran (a mix of 5)/carom seeds/fennel seeds
2. Turmeric, ground powder or fresh root, both giving different flavours.
3. Ground coriander seeds
4. Chilli powder/chilli flakes
Extra, Following would be nice to have. Grind both fresh, the difference in flavours is amazing.
1. Cumin powder, fresh and made from dry roasted seeds.
2. Garam masala. Make your own (recipe on my website), the difference is amazing. Some dishes use whole, generally added to hot oil at the beginning of the recipe. Most dishes say sprinkle at the end and close lid, so flavours can develop and infuse. Make your own (recipe on my website), the difference is amazing.
If you have these things, you can make almost all Indian dishes.