Let me try to clarify this in set-theoretic terms. Some people say they see things in three spatial dimensions. Therefore, we can conceive of, say, a recently born baby who has not yet built up that mental infrastructure of spatial relations. His 'visual' sense data are a disordered set. Well, if we wanted to be pedantic, we could say that the unordered set is a 'form', but it would be truer to the normal usage to say that it is the absence of any form.
Form is dispensable.
Although Berkeley did not explicity discuss this at a theoretical level, his comments on the Molyneux problem suggest that he would concur with what I am suggesting here. Hence, I feel justified, when I am developing what I claim to be a Berkeleian theory of mind, to suppose that sense data are primarily formless, and that the forms that we take for granted are constructed by the mind by means of volitions and the sense-data themselves. You mentioned causality as an example. In some ways, Kant was right about causality and in some ways he was wrong. A common view, and one that I think you are espousing, is that naked phenomenology can give us nothing to work on for understanding what makes the world tick.