I'm a fan of Kitchen's of India.
Cheaper than the jars usually and makes much more. You just need some butter and some milk. Put in some coconut milk if you want (recommended).
I usually just fry some chunked up chicken breasts with some variety of bell peppers, onions and garlic in some coconut oil. Sprinkle a little curry powder on the chicken/veggies.
Meantime heat up the milk/butter/paste and once the chicken is done just toss all the fried stuff into the pot with the sauce and let it simmer stirring occasionally until it's the thickness you want.
Honestly usually tastes better as leftovers after it's thickened up in fridge overnight.