It depends on what version of the Enclaves you go with.
When they first appeared in the original 3rd edition Codex: Tau (hallowed be thy name), the Enclaves did not include auxiliaries. They had far less resources than the Tau Empire did, so the general reasoning seems to have been that they were too poor to hire Kroot mercenaries (this being when even Kroot working for the Tau were largely motivated by tangible reward), the only auxiliaries available in the codex at the time. For similar reasons they also weren't allowed to take Gun Drone Squadrons, and everything else except Firewarriors, Devilfish and Crisis teams was restricted to a 0-1 choice (which meant that you could only field a maximum of one Fast attack and two heavy support choices in the entire army). They also couldn't include Ethereals, but that wasn't because of their resource shortages.
Later on in the 4th edition codex they still didn't feature auxiliaries, being unable to field Kroot or Vespids for... reasons. It was still included in the Breakaway Faction special rule that enforced these restrictions (and that I actually really liked, believe it or not. It gave a great guerrilla army vibe to Enclave armies), which had been expanded to include the new units the 4th edition codex brought with it, but Kroot aligned with the Tau were starting to be depicted as being more ideologically motivated and less interested in cold hard payment, and Vespid were voluntary members of the Tau Empire with ideological motivation right from the start, so that explanation no longer really worked as well. GW writings at the time, as well as fan theory, seemed to suggest a Tau-supremacist edge to the Enclaves at the time.
Then at the time of the 6th edition codex things started to change. The Enclaves, which up until now had been Tau with extra grimdark added in (seriously, the old-school 3rd edition Enclaves were extremely dark and shady), were effectively retconed to more explicitly fit a more heroic image of an underground freedom fighter movement. Under this depiction the Enclaves did include Auxiliaries and I believe the Enclaves expansion book has an entire Enclave world given over to Gue'vessa. Under this depiction they also have a lot more stuff at their disposal, supplementing their own resources and industrial base with goods and technology begged borrowed or stolen from the Tau Empire.
So it's down to what version of the Enclaves you prefer. Personally I prefer the dark shady Tau Brotherhood of Nod that the 3rd edition Enclaves were, and that's what I generally go with for my Battlefleet Gothic background, but others have their own ideas.