Stormfeather gave u the basics on the stockpiles. "Stone" (subset "metal") is the input for smelting and "Bar"s are the output. I think the best advice is to try and use a specific forge for a specific metal, whenever practical, and have a very small stockpile for the input (i like 2x3), restricted to ONLY that type of ore. I have a bigger Bars stockpile set to take only metal bars (plus coke and charcoal bars). If you don't restrict the bars stockpile near the forges, haulers waste time and space filling it with all sorts of things like stone blocks and bars of soap.
Did you 'b'uild the cages to get them there. If so, use 'q' on them, then 'x' to remove. They'll be moved to an animal stockpile which has 'empty cages' allowed. I make a stockpile JUST for empty cages, near the trap area, and disallow empties on every other animal pile.
My favourite method for dealing with caged Goblins is pretty standard, you know most of this already I think but i'll lay it out anyway.
I have a Goblin-only Animal stockpile, with hatches over a pit, basically as shown below, but bigger, the idea is that each goblin cage is next to a hatch, and this way they're dragged straight from the cage trap to the pitting area with no building or levers required. Channel the holes first, before creating the stockpile, then define the pit to cover at least all the holes, and add hatches to the holes. Important : ensure this is the only stockpile which accepts Goblins. If you hit page-up about 5 times in the list of possible caged animals, you find the Goblins entry, btw.
GGGGGG G=goblin cage stockpile square
GHGGHG H=basic hatch
GGGGGG
GGGGGG
GHGGHG
GGGGGG
BTW, NEVER skimp on the pit hatches, I did and regretted it, as half my dorfs got scared and trapped themselves on the pitting level, while I waited in vain for my 8 marksdwarves to finish off maybe 80+ pitted Goblins out of 140 total (this was two or three sieges worth of Goblins, i was starting to have a wood & cage shortage, frequent sieges, and was in a hurry). I only avoid mass-starvation / dehydration by creating squads out of off ALL my 160 dwarves, and ordering them downstairs, then putting an alert on and ensuring that the pitting level was a no-go zone. Result of being in a hurry : A huge waste of time.
I do the d-b-d thing to mark all cages for dumping, then use the 'k' cursor and click 'd' on each cage so as not to dump the cage itself.
Then, I station close-combat troops in the middle of the cages, and below there's the pit, with at least 1 wall made of fortifications, and marksdwarves lined up to shoot any pitted Goblins (they have to be in a thin tunnel next to the fortifications, or use traffic designations to encourage them to stay near it, otherwise they don't shoot).
Once all items are dumped from the cages, and the troops ready, I order all Goblins pitted. The melee troops kill anything which escapes, and the marksdwarves kill the pitted ones at their leisure (can take a while). The cage stockpile above the pit only accepts Goblins, so once they are pitted, a dorf automatically hauls each empty cage to my empties pile.
I find this system to the the quickest and best of all i've tried, and it's good for training troops too.