Frankly speaking, there aren’t any good privacy coins that are not well known. If you are looking for privacy coins that are not as expensive as Dash and Monero, Deeponion is one good privacy coin. Supply is limited and price is still cheap at the moment.
Dash and Monero can be tracked, but with a dark GBYTE to do it will be much harder. About ONION I can not say, did not penetrate much and no desire. ONION I personally do not like