The lightness of a cake is a direct consequence of how much air you get into it at the beginning. Sift your flour from a decent height, cream your eggs and sugar until really light and fluffy and be very gentle with your folding in to prevent knocking out any air.
for years all my cakes turned out heavy - you could build houses with them! many years later I found that if I added an extra teaspoon of baking powder to the mixture and then bake, they turned out lovely
I`ve never manged to make a decent sponge they have always turned out like biscuits. Mum was fantastic at making them & I`ve even made one exactly the same as here at the same time.....still biscuits !!!!