Your question already carries an intention to begin. So in The Magician, I would first see the ability to give an idea form: choosing what to draw on and where to direct your efforts.
Your tools are already within reach
The symbols of the four suits lie in front of The Magician. For a question about starting something new, this image can be read as an invitation to look around: what do you know, what can you do, what do you have available, and who can you turn to? You don't need to have everything at once. What matters is noticing what you can realistically start with.
Let your idea meet reality
One of The Magician's hands is raised toward the sky; the other points to the earth. This gesture can suggest a connection between an idea and bringing it to life. Perhaps your idea now needs a first try: a sketch, a conversation with someone who might take part, or a small sample of your work. That step will give you both a result and a better sense of what needs refining.
Make a promise to yourself you can keep
The Magician's willpower invites you to think about where to direct your efforts. What one action are you ready to see through? Let it be small enough to carry out and meaningful enough to bring you closer to what you have in mind.
In the context of your question, The Magician can be read as this advice: start with what you already know how to do and find a concrete way to use it.