A bit like the advice given to me about making curry from a pakistani friend who was on my course at uni.
Lots of finely sliced onion, a can of chopped tomatoes, fresh ginger and garlic (as much or as little as you like though a teaspoon of each seems to be about right), chilli (fresh or dried, it doesn't matter, again to taste) and a really good garam masala. And marinate your meat overnight in plain yoghurt if making a meat curry, or add the yoghurt as a finishing touch when making a vegetable curry. If you're feeling flush, throw in some cardamom pods and cassia bark during the cooking - long and slow is best.
She said to me that it'll taste like a good curry regardless of what goes in it. And you know what, she's right. 25 years later, I still make my curries the same way.
Edited to add: if the sauce needs thickening, add some ground almonds or some creamed coconut.