1. I bake by weight as I find that gives the most consistent results, especially when baking gluten free. One cup of your gluten free flour blend may not weigh the same as my blend, all the commercially available blends have different mixes and ratios of flour in them. I’ve weighed cups of different blends of flour and noted that a cup of gluten free flour can vary in weight from 125g up to as much as 170g depending on how you scoop it, and what type of mix you use. You can see how this could drastically alter the outcome of a recipe.
I recognise that most Americans are used to the cup method which is why I also include those measurements,but they may not give you accurate results. If you are a keen gluten free baker I would encourage you to invest in a scale, you can get one for only $10 - $15.
2.I prefer to use my own homemade gluten free flour blend as it's cheaper and I get really great results.
3. If you can, avoid buying flour with gums already added. The reason for this is that you have no way of knowing how much gum is in there and that can alter the outcome of the recipe. So for example, too much gum can give you a more sticky texture in a cupcake. And though the cupcake recipe will still work, it won’t be as nice as if you measured and added the gum yourself.