Depends on what kind of sauce you want.
The usual sauce that we use for our curries (like paneer butter masala, chicken butter masala, etc.) is this -
4-5 cloves of garlic (small-sized bulb)
Half a teaspoon of ginger (finely chopped)
1-2 tomatoes (diced and de-seeded)
1 medium onion (chopped)
2-3 teaspoons of oil
Pinch of mustard seeds
Masala mix: 2-3 teaspoons of coriander powder and 1-2 teaspoons of red chilli powder
Heat a wok and add the teaspoons of oil. When the oil is hot, add the mustard seeds. When they've begun to crackle, toss in the ginger. Saute a bit and then add the garlic. When the garlic turns a light shade of brown, add the onions. Cook the mix for a while until the onions start to cook. Then add the tomato. Add the masala mix and stir well. Add salt to taste. If you want your sauce to be spicy, feel free to add more red chill powder or toss in one or two green chillies (de-seeded). Turn down the flame to low. Cover and cook the mix while occasionally stirring it. (Optional - you can add a little bit of water depending on how thick you want your sauce). After about 10 minutes of cooking, check if the mix is thoroughly cooked (the flavour must be consistent). Take it out of the wok and put it on a plate. Let the mix cool down to room temperature. Then mash it in a blender. Add in a teaspoon or two of water to maintain the consistency.
This is the basic sauce for most Indian curries.