BLM dual wielding shouldn't have any issues spamming moonlight if you need mp, since you're getting insane TP return with kraken club. This assumes Aspir isn't applicable. Also, idling in Mallquios Clogs+2, Ethereal Earring, Kaumodaki nets MP return
BLM/DNC means Bunzi/Maxentius (not KC) at least ...before Bonanza Weapons were given out to everyone.
The comment above first mentioning dnc sub says Kraken Club offhand, that's why I mentioned that. Even still, you can Moonlight with Bunzi/Maxentius. Anyways, what Nariont said is accurate, and you can also use Blurred Staff +1. You can get fast TP, Myrkr when you need MP, and self SC due to the OAT on the staff (which also provide free self-Haste).
I have said it before in other posts, but MP management on BLM is seriously not an issue (neither is it for RDM or GEO). If you are running out of MP on BLM, you didn't manage it properly, don't have weapon swaps for Myrkr, didn't bring meds, don't know how to use the tools at your disposal, or don't have an emergency AF+3 MB body macro to refill mana.