I would recommend that anytime you invite faeries to your workings that you have them remain outside the circle. Even when they have the best of intentions, their mischievious natures have been known to get the better of them. At the very least they can be distracting. Allow the energy they help to generate into the circle, but it is best to let them play outside, so to speak.
I am not a believer that a circle must be cast formally, nor that it be cast the same every time you cast it. A circle may be cast with simple visualization techniques, or with a large, complex formal ritual. Neither method is better than the other, though each is suited to a different style of magick. most practitioners work within a happy middle ground, either leaning more towards formal ritual or towards loose visualizations.
The stronger your visualizations of the circle, the stronger the circle will be, allowing you to draw and direct more energy towards a working. So perhaps it is best if you begin in that happy middle ground between formal ritual and pure visualization, allowing a ritual to help you in your visualization of the creation of the circle, but without the ritual being too complex for you to visualize. As your skills at visualization improve, you will wish to move either toward more formal rituals, or to more pure visualizations, whichever is more comfortable to you.