The crucial thing is to adjust your clothes to the season and various weather conditions. A cap or hat, fleece sweatshirt, waterproof jacket and trousers of quick-drying material will definitely com in useful. Even in a hot, boiling day the weather can turn cold and rain can come down.
Rivers often flow in deep, forested valleys that are shady and cool, even during summers. And some other stretches are very sunny, so you have to be prepared also for intense heat. It is better not to take jewelry on trips, as it can easily catch on branches, and your glasses should be equipped with a string or rubber band. Best footwear will be water shoes (they are cheap and can be bought at any superstore). Flip flops or slippers are not recommended, because they are easy to lose and can cause injuries.