How can I quickly save an unflavorful curry?
Indian curry traditionally has - in addition to the ginger, turmeric, cumin and chili (I assume you mean chili powder) that you used - a generous amount of garam masala, coriander powder, and garlic.

Sometimes you'll see "curry powder" used in recipes instead of garam masala; they are similar but not exactly the same.

Either one of these would be fine, and arguably the most important missing ingredient here. I'm not even sure you could legitimately call it a curry without one of the above.

Depending on your spice tolerance, you might need to add more chili powder as well.

Note that most spices in a curry will need to be heated before they'll really release their aromas (and therefore flavour), so you can't just add them cold, and I definitely don't think you'd want the taste of raw garlic/ginger in your curry, even if it is presently tasteless. Give it a good simmer after adding some garlic (powder is fine) and garam masala or curry powder and you might be able to salvage it.

Or you could try heating the new spices dry, for a very short time, to give them a bit of a head start aroma-wise; just be very careful not to burn them.