Ritual starts with the "purification of self". In many paths, this includes putting on robes, washing or bathing, or performing ritual cleanliness steps.
In place of these things, we don our Witchself. Our Witchself is - essentially - a mental image we have of ourselves as a witch. Folk new to the path spend some time developing this image, perhaps with a moodboard, or through doodling, or reflecting. Or, if you tend to get clear messages in meditations, by meditation and asking for insight. You are encouraged to be a SHAMELESS MOFO in developing the coolest witchsona EVER, which 12-year-old-goth-Wiccan you would have keeled over and died of envy to become. That's the part of yourself you are contacting here. The teenage you who wanted to be a witch.
Your witchself can be a Celtic-boho-longhaired wild woman; a 90s black-gloved punky Pagan; a formless void with shadows like great wings; whatever you like. Whatever you find powerful. Witchcraft is about becoming, about claiming the power that is yours by right of birth. Witchselves do not have to be human, or animal; they can be any gender, any age; but don't be over-proud (don't make your witchself "I am the goddess the Morrigan", because that ends well for nobody). You can develop several witchselves for different purposes, in time, but one will do to begin with.
Our path is inherently about shapeshifting as a form of discovery and power. By taking on the trappings of your witchself, you also take on that self's power and confidence, in a way that reflects back into your everyday. Collecting suitable items of clothing - not necessarily a robe - and accessories is part of preparing to become your witchself. If your witchself is very conceptual, you could also find films, music, foods, decor, and so on - anything which helps get you "into the zone". At the same time, these are just props. You can do it without them. It's good to attend to the psychodrama of witchcraft where you can.
Before starting a ritual or spell - or at any time you need to draw upon your inner self - don your witchself. This stands in place of ritual baths and ritual cleansings.