Indian cooking - How do I get the consistent taste
Perhaps you couldn't get definite answers because there aren't any...


You can't get a consistent taste every time: your basic ingredients won't be the same (different stage of development for vegetables, possibly different varieties, not always the same freshness, etc.), and neither will the fresh spices like ginger and garlic, or things like yoghurt. With experience, you can somewhat correct for this, but never completely.
You probably don't need all the 12 spices, but they each add something to the final taste (or appearance: turmeric and dried sweet pepper come to mind). Leaving out some of the minor ones won't do much harm, but might make you wonder what's missing. 


Also, the same spice might get added twice: e.g. cumin: once whole, and fried in the hot oil, then ground just before the simmering stage. And that will give two different "notes" from the same spice.