My own coffee and a crystal wine glass - two absolute essentials! That's first. Then, a brand new project and an old one, enough fabric to work with, matching threads, machine WITH power lead AND foot pedal, spare globe/needles (machine & hand)/bobbins/pins, scrap fabric to test stitch on, plastic/wooden finger presser, herra marker, air fading pen/chalk/marker, lead pencil, fabric eraser, templates/template plastic/heat resistant mylar and basting spray/pins etc. Applique supplies if appliquing/paper piecing supplies if paper piecing and at least one fancy gadget you can talk about/show and tell if you want to. Depending on what you're doing, you might wish to take 505, spray baste it or similar. These are the things in my kit - I don't need to take rulers but I do take my own rotary cutter. Make sure it's all marked CLEARLY with your name. Now if you have any room left, you could add mini iron mini cutting mat and block book.
I have these things (apart from the project pattern & fabric) all packed in a bag ready to go as I go out to quilting once a week and this is my essentials list. One bag for applique another for regular and paper piecing. They stay packed with the spares and I just add the project to the bag and pack up my machine. It works well for me as the bags double as storage too. HTH - have a fabulous time!