Adhesive is the whole product. Everything else is decoration. Cheap pasties fail in heat and humidity, which is exactly the condition most people wear them in. If you are going to be outside dancing for hours, buy the better pair rather than two cheap ones.
Apply to clean, completely dry skin. No lotion, no oil, no body shimmer, no sunscreen underneath. This is the single most common reason pasties fall off, and it has nothing to do with the pasties. Press for thirty seconds with a flat palm, do not rub.
Size to your coverage, not to your bust. What matters is the diameter of the area you want covered, not your bra size. Measure once and you will know your number forever. If you are between sizes, go larger, because an edge that lifts is what people notice.
Nipple piercings need a plan. Flat-backed jewelry sits fine under most pasties. Rings and larger barbells create a raised point that lifts the adhesive, so either size up so the edges have flat skin to grip, or swap to flat backs for the night.
Removal decides how many wears you get. Peel slowly from the outside edge, never fast from the middle. A warm shower first makes it painless. Then put them straight back on the plastic backing they came on, which is what keeps the adhesive alive.
If the adhesive stops gripping, it is usually not dead. A rinse in cool water with a drop of mild soap, dried face-up and not towel-dried, will bring most reusable pasties back for several more wears.