As a coeliac, if I’m baking for myself, I have to use gluten-free ingredients. Fortunately, nowadays, gluten-free alternatives are so good that it is barely a consideration when baking cakes. I keep gluten-free plain and self-raising flour in my stock cupboard and they work very well in most recipes as a direct substitute.
Biscuits are often more crumbly and pastry poses a particular problem, since gluten is the stretchy bit that binds things together, so without it, hard things have a tendency to fall apart. The addition of some egg to pastry and extra butter/milk in biscuits goes a long way to solving this problem, although I have not yet been able to make really good gluten-free pastry – if you have a wonderful recipe, please let me know!
Wherever there is a need for gluten-free ingredients, or where a recipe is naturally free of gluten, this will be specified to help you.