Poke coins at http://treatz.me/ should never be wasted. You can buy various items with the poke coins for example poke balls, incubators, incense and lure to attract the Pokémon species. It should be used to buy rare items that you cannot get from a pokestop easily like incense and lures. These are used to attract the Pokémon towards you so that you can easily capture them especially a wild Pokémon. Instead of running around to find out where the Pokémon is the lure and incense bring them to you. But at the same time these items should be used efficiently. With unlimited poke coins availablethere are no restrictions on how to use these rare items too.