Here is a list of some essential spices for our members who are new to home cooking:
Cumin seeds
Coriander seeds
Turmeric
Chilli powder
Kashmiri Chilli Powder
Cinnamon sticks
Mustard seeds
Tej Patta if not then Bay leaves (but they are not the same)
Cloves
Black Peppercorns
Green Cardamom Pods
Black Cardamon Pods
You can make home made Garam masala using spices from the above list.
Kasuri Methi
Nutmeg
Fennel seeds
Fenugreek Seeds
Ajwain Seeds
Paprika
Amchur
Tamarind
Chaat Masala
Kalonji / onion seeds
Crushed chilli flakes
Mace
Paanch Phoran
Star Anise
There are other spices too but you can build them slowly otherwise this list would go on forever.