I always use my own spices, and have gotten pretty good at varying the proportions to get different effects. Whole spices make a world of difference - they are so aromatic!
I start by toasting some cumin seeds in a hot, dry pan. Then add oil and saute onions, garlic, and maybe ginger. When the onions get well cooked, add some water and let it simmer. I grind coriander, cardomom pods, crushed red pepper, and maybe a few cloves or asafetida seeds in a spice grinder and add it in, along with some turmeric. You can drop in a whole cinnamon stick too - Cook it for awhile - the idea is to let the water boil off to make a thick, concentrated, almost pasty sauce. You can add some tomatoes at this time to give the sauce a better consistency. Let it all cook until it is pretty smooth and mushy. Then add your veggies, some more water if needed, and simmer until the veggies are cooked how you like them. I like to add currants and pine nuts too. You can stir in a little soymilk or vegan margerine at the end to make it creamier. Also at the end, you can add green herbs like perhaps a little cilantro or some fenugreek leaves.
Experiment to get the blend of flavors you like. If I'm doing two curried dishes for one meal (dal, say, and also a vegetable curry), I emphasize cinnamon, pepper, and hot spices in one of them, and cardomom and maybe ginger in the other. They end up tasting like completely different dishes, even though the basics are pretty much the same.