Neutrals don't draw attention the way other colors do, but you need them! This is a nice set that includes lights, mediums, and darks in colors that lean gray or brown.
I like Efina from Wonderfil a lot. I'm using it for hand piecing right now, but it's also a wonderful option for hand appliqué.
Efina was developed for hand appliqué. It is a 60wt 2-ply 100% Egyptian Cotton, made exclusively from the highest calibre extra-long staple Egyptian Cotton. Efina is strong thread that is uniform in diameter (no lumps or bumps) with a visible twist.
You might want to add Parchment, an off-white not included in this set.
Efina colors included in this Neutral Bundle: Pearl Grey (1), Grey Flannel (4), Slate (5), Latte (2), Saddle (29), Chestnut (51)