Preparation in clothing is important because you have to feel comfortable with the clothes you wear, so that nothing distracts you when performing the ritual.
It is usually recommended to use light colours such as white or beige, so that the energy flows.
No less important is your inner preparation, basically your predisposition to do the rituals, cultivating your spiritual part implies being willing to perform the rituals with faith. There are people who relax drawing mandalas, others listening to music, etc.
Either way is valid, the important thing is that you feel predisposed to do magic.