You will be put on a clear liquid diet for a time period determined by your Doctor so your diet will be simple.
In regards to clothing make sure that you yield to comfort rather than fashion. You do not want to do or wear anything that will make your experience any harder or complicated than it needs to be.
This procedures are very unique to the person and while some experience very little discomfort it can vary on a personal basis.
Best of luck to you and welcome to a new phase in your life. It is well worth it.