Well, I'm also new to MW but have managed to get a hold of most of the buildings in my experimental fort now(except the freaking chemist and magic school since my researcher keeps failing that for some reason and the really advanced stuff that requires magma as I've yet to reach the magma sea, so much stuff to do) but IMO the most useful are:
1. Alchemist, which can make you that bloodsteel quite cheaply, you only need bones, ash and blood, which after a siege or necromorph apocalypse are in abundance. Bloodsteel armor and weapons are awesome to have early on and later if you, like me, don't bother with mining as much as experimenting with different workshops
. Just make sure to make a loot of blood barrels from any meat you have and you'll have great fun
2. I'd advise against making metal bars from ironbark and steeloak logs. Just use the logs themselves to make weapons and armor, they work just as well as the real metals, I found that out when using a danger room with 1 steeloak training spear and 1 ironbark spear. That mithrill-clad recruit stood no chance.... The best use for the herbalist I've found is making glue from spore trees, an item you'll need a lot of to do research and make the libraries, as well as copy your completed research. I don't really know if those youth potions and what else is there work.
3. The alchemist is also great to get the materials for welded materials that you make in the metalsmith. I'd advise you to make a LOT of welded armors and weapons they're awesome if you happen to have a lot of a certain ore, like I do cobaltite.
4. If you get a hold of some glumprong trees, process them at the sawmill to get their acorns and make a huge farm with them. Then you can farm blood like mad
. Same applies for feathers which you'll need for quills, again for research.
5. Stockpiles..hmm, well just make dedicated spaces for each lab and link the raw materials stockpiles(ie blood stockpile, bone stockpile, bar stockpile, cobaltite stockpile) to the lab, and a huge main finished goods/bars stockpile that only takes from the labs.
6. The toxicologist should be a great weapon enhancer method. Unfortunately I have not seen the results as I got the lab after the latest huge massacres. Just unequip your soldiers of their weapons, place the weapons stockpile near the toxicologist, make the lab take weapons only from THAT stockpile and coat them in shadowleaf or bitterroot since those are cheap and easy to get in massive quantities(hey I even have shadowleaf pies if you can believe that
, oops settings
)
Cheers