Crinkle Cotton is a comfortable fabric for hot summer days. The micro pleating provides stretch and the natural fibre is light-weight and breathable. The side story of many summer whites is they are sheer and the modest may worry about undergarments showing through. A good choice then is Very Easy Vogue pattern 8656, which is a mid-thigh tunic (reminiscent of a school uniform) over wide-leg, elastic waist pants. The long tunic covers the seat of the pants completely, giving the wearer an extra layer of cover.
Of course, pre-wash your fabric before sewing and steam out any creases rather than pressing. Do this by hanging up the cloth and aiming the blast from your iron vertically. You don’t want to flatten those perma-pleats.
Resist stretching the width of the fabric when pinning and cutting the fabric, you will want all the pleats in relaxed mode, as that is how it will hang when worn.
Stay-stitch around the neck and armhole openings before attaching the inner binding; you are aiming for a non-stretchy neck edge so it will never gape.