-You were using far too many mining ships, and not nearly enough transports. From our mining group's time in the tau's, I've found that the best profit comes when you use 1 mining ship (an actual mining ship, not a spatial or mafic) and 1 4-5k trade ship. A single miner can generally mine up 4k worth of ore by the time the trade ship goes to and from the selling point - so any more is really overkill. Further, the more people involved, the less money each person is going to make in the same amount of time. Now, if you had 8 mining ships and 8 transports, things probably would've been more profitable for everyone involved.
-Gold isnt one of the better-selling ores, in my experience mining with the new system. Generally speaking, if it doesnt trade well, it doesnt mine well. I rarely made more than a few million a run trading gold, and I only hauled gold when I needed to get to somewhere else for more profitable cargo. Diamonds, niobium, etc. are far more valuable commodities to mine for.
-Trade ships do not really need to be allied to the mining players, unless you're in an actual mining faction with a set tag and ID. With our mining op in the taus, we use junker trade ships, because they are less susceptible to pirates and neutral with the majority of faction npc's you're likely to encounter.