These are some of my favorite cross stitch supplies that I use on a regular basis:
Needle Threaders - My favorite at a low cost, too.
18-count Aida - This can feel a little stiff, but the price is hard to beat.
https://amzn.to/319gPC828-count Evenweave
Thread organizers - You can see these in my Stitch With Me videos
Labels for my thread organizers
Pen for gridding fabric.
Rings to hold my thread drops for organizing my floss
Cable loops for thread organizers
Good to have nearby:
Favorite desk/supply organizer