You create a spell similar to if you were creating a recipe for cooking. Nobody, i would hope, jumps in and attempts to make something from scratch without prior experience (and not following a recipe - but creating one). No, you do not have to be "super" experienced, but experience is a plus. For many practitioners, when they start out, they really have no idea about the ethics or purpose of a spell. They do not understand its usefulness or purpose. However, over time each practitioner develops a sense of what those things are, thus allowing them to understand how a spell is/was written. Remember, all the spells you see were written by people (like you and me).
I suggest you take it on yourself to read about the ethics and purpose of spells. Search the internet, look in books. My first book that i still have to this day is Power: Spellcraft for Life by Arin Murphy-Hiscock. The book gives nice and understandable explanations to the purpose and ethics of spellcasting.