A summer bed is an exercise in taking things away. The instinct is to add a thinner blanket; the better move is to remove whatever traps air against the body.
Start with plain-weave percale in a pale shade. Percale has no float, so air moves through it, and the crispness you feel on the first night is the same structure that stops it clinging.
Over that, a three-layer muslin dohar and nothing else. It gives you the feeling of being covered without the insulation of a quilt.
Wash new percale before first use — it softens measurably in three cycles — and rotate pillow covers twice a week. Body oil at the pillow end is what yellows cotton first.