First off, I feel your pain. In older versions, you could get just about any metal in existence on one map. Now it's far more difficult. But here's a few things that might help.
- Finally, remember that there is one source of iron that doesn't come from underground at all. Goblinite is plentiful, and all it requires is preparation and patience. I myself am building a minimal-digging above-ground fortress that is sitting on a huge pile of limestone, but with absolutely no metal ores at all. When the first few goblin ambushes come along, I will grin like a madman as I order the levers pulled.
This is assuming one very crucial detail: that your goblinite is, in fact, iron. My goblins in my most recent fort only bring copper armor and silver weapons. Nothing else, period. Never rely on "There's always goblinite" these days, because if the goblins haven't found it in their fortress sites, their civ will not have it, same as any other.
Your best bet, as stated, is to try and find a sedimentary area. Look for overlapping biomes around a river with "shallow metal" or better yet, "shallow metal
s". If you settle on overlapping biomes, both with shallow metals, around a river or stream, it is VERY likely you'll get flux and iron at least somewhere on your map. Until the caravan arc is finished, careful site hunting or modding are your only options.
Another tip: if your parent civ and the humans have access to iron, buy ALL the crafts and armor you can from them, then melt them down into iron. It's expensive, but a single skilled stonecrafter can churn out more than enough stone crafts to buy them out (bring a bone carver and some dogs for a cheap and reliable access to yet more crafts). You can also request iron bars from your liaison. This method is slower, but unless your fortress is massive and needs a huge military, you should have enough iron to handle the necessities, particularly if you have sand and magma safe stone (to eliminate the need for iron to handle magma projects).