We do not get garam masala readymade here neither do we get all the spices needed to prepare it at home. So here is quick version with the things we get here.
1. 2 tsp of coriander powder
2. 1/2 tsp of cumin powder
3. 1/4 tsp of cinnamon powder
4. 1/8 tsp of clove powder
5. 1/8 tsp of bay leaf powder.
Mix all and transfer into a small box. You can obviously make a larger batch, but if you are new to indian cooking the above amount is sufficient for a couple of days.
All the above powders we get here readymade, they are raw powders not roasted.
If you have none of them at home right now, minimum needed is coriander powder and cumin powder for any recipe which asks for garam masala.