No one can truely say when the best time for you to cast a spell is. I suggest that you put a serious amount of time into studying magick and all it's facets. The more you know the better prepared you will be. Knowing what magick is and how it works will also help you avoid wasting time on spells that are fake. It will also increase your understanding of what you are doing and why, which alleviates the fear or feeling that you have done something wrong when you do cast a spell.
Spells work better, in my opinion, when you write them yourself. Having done the above will help you to understand how to write a spell, which will increase your understanding of how and why they work.
Practice, Practice, Practice. When you have done that, do more of it. This is a life long path there are no shortcuts