This is just a basic guideline for low-carb baking - and some may find that these measurements may be a bit much - it's all in your personal taste -

1 tsp. xanthan or guar gum per cup of flour for cakes
2 tsp. xanthan or guar gum per cup of flour for breads or pizza
1 tsp. or no xanthan or guar gum per cup of flour for most cookies

as for the baking powder, be careful - believe it or not, too much will actually cause your baked goods to sink/collapse and they'll be dense & heavy. use a scant teaspoon per cup of flour