Good advice there, and I will add one more. If you have some bits you already own, snaffles, try them first. Try in an arena or round pen, and become familiar with the horse. You can also try some short shanked solid mouth (with some tongue relief) bits, if the horse is expecting poll signals.
And if you don't already own what works for the horse, find a tack store that carries Myler bits, and chances are they will do bit rental. I am a Myler dealer, but do bit rental on every brand of bits I carry.
The bit rental program is so you can try the bit on your horse and in your riding conditions before you commit to buy a bit. Sure helps.
I ride all my gaited horses in a medium port bit, two in a snaffle of said mouthpiece, and one in short shanks. Long shanked bits are not required for gait, although your horse might expect a long shanked bit.
Mostly, no matter what bit you end up with, take some time in an arena setting to just get to know your new horse.