To avoid overly dense cake -- most flourless cakes depend upon stiffly beaten egg whites or other self holding leavened agent.
Beaten egg whites should be folded in as soon as they reach proper consistency, do not let them sit.
1/8 t to 1 egg white: When using cream of tart to help stabilizer your egg whites remember this ratio in order to avoid egg whites from breaking down or getting too dry: 1/8 t to 1 egg white
Why I don't use gums and don't recommend them:
1) they are expensive
2) they reduce the aeration of products
2a) reducing volume
2b) less smooth and butter texture
When replacing flours sponge cake and cookies prefer easily dissolvable starches with a percentage of around 9.8% (see flour comparison chart)
A bonus for bleached flours -- the bleached flour acts like a roughened surface allowing more stick -- i.e. roughen surface before gluing two pieces of wood together. This better stick allows for better suspension and gelatinization -- important when using gluten free flours since, well, there is no gluten to help produce this effect.
Keeping these tips in mind your cakes are more likely to stay aloft, rich in flavor, and much easier to make.