Please do not spray any chemical, deodrants, perfumes etc directly on the gemstones. Some gemstones are really fragile and such chemicals may harm their lustre, sheen or even the skin (surface) of the stone.
It is always advised that you open the clasp and then wear the beaded jewellery. Excessive pulling off the elastic or the thread may lead to its breakage. Continous usage in water (eg wearing while bathing) may cause the thread to become weak. It is always better you remove them that time.
Raw gemstones/crystals can be cleaned with any light oil. It cleans off the dust and also brings in the shine of the gemstone.
When you have a lot of gemstone strands together. Some stones might rub against each other and damage the gem. Kindly keep them in between cloth or wrapping paper/pouch.