For men, what to wear is less of an issue than it is for women. Normal trousers and shirt, T-shirt or polo are fine. Make sure they are lightweight and natural fibers – cotton is best. Polyester or any similar artificial fabric will become uncomfortable very quickly.
For women, a basic wardrobe would be loose cotton or linen trousers and/or a longish skirt and cotton tops with sleeves that are at least half-length. It is useful to carry a pashmina, chiffon scarf, or shawl to help with covering up when you go to sensitive places, such as temples or mosques; to protect yourself from the sun, or if you find yourself amongst a group of ‘admiring’ men.
You will need ‘practical’ shoes. The roads and pavements are not tremendous (but improving in places) and to get to many of the sights you have to trample over the unmade ground. Comfortable shoes or trainers with sturdy soles are best. Sandals are OK in the hotels and on cruises, but there is lots of sandy dust so they will become uncomfortable in town. When the coarse sand gets into sandals it can very quickly create blisters.