Only epic troop token ( gold color ), has a chance of 4* troops. Based on RNG you could go months or years without a 4* Troop. Once you get a 4* Troop, you could go decades without a rainbow set of 4* troops.
Generally 3* lvl 10 troops = 4* lvl 1 troops and 3* lvl 20 troops = 4* lvl 11 troops so I would concentrate on your 3* troops for now.
