Yep, the spice mix and chilli should go in before the base is added and fried until aromatic. Garam Masala should be added a few minutes from the end of the total cooking time, and like BB pointed out, a tablespoon is way too much. I usually add a pinch, or 1/2 a teaspoon MAX.
All based on trial and error, and the findings of others on the site.
-- Josh