It's all RNG, someties ive gotten 4 CTMS from one raid, never seen any more for a month. Similar applied for rarecandies.
Im hoping for PvP, they add some sort of candy gaining feature, emulating how in the main series pokemon level up from battles. Maybe this meter would fill by not switching a pokemon out from a battle team like a walking buddy or something and measures cumulative CP beaten to prevent pidgey battle spams.
TM's would be a nice addition, but they'd probably be really rare.