You may use coconut oil or a mix of ghee and oil for the tempering.
The ingredients that go into the tempering is totally your choice, add or deduct as required.
We like the soft upma, but if you prefer drier, then use 2 to 2.5 cups of water for each cup of semolina. Tinker with the water quantity till you have your consistency. :)
You can dry roast the semolina and boil the water in the tadka instead. However, I prefer this way, since I feel the rava gets a lot of flavor from the ingredients.