For me the #1 must have is a good comfortable, adjustable chair.
After that, plugs where you need them (not where the builder decided they should be back in 1923!) plenty of shelves, various sizes of clear plastic storage boxes, lots of pins (both yellow headed straight pins and safety pins of various sizes), several pin cushions (in various places), a good iron and a larger ironing board than the over-the-door one that I have, and nobody else using my space for anything else!