Professions are useful in several ways in the game. This series of posts deals with what we can do to help our SH grow however, so we'll be looking directly at that.
There are several tasks available that build donatable items, but only a few that are of ongoing use. The tasks for creating surplus EQ objects are generally not worthwhile since other sources are cheap. Lets take a look at the ones that will save us a lot of AD, those are...
Leadership has always been useful in Neverwinter, but the uses have changed over time. Its generally good to level it for the RP alone, but it can also be used to help build the SH. Several of the structures take AD Chests. There is the option of donating Astral Diamonds directly, however that is hideously expensive.
Leadership can create a Crate of Astral Diamonds at level 23. This should be run as often as possible, by as many characters as possible. The task is free to run, and over time can fill all the necessary AD requirements for the coffer.
Jewelcrafting: Jewelcrafting is good for making rings and high end MW materials. It also has a use for the SH. Many structures require gems to be donated. One can donate RP directly however this can be fairly expensive as well.
Jewelcrafting can create a Crate of Precious Jewelry also at level 23. This should be run at the same time as the AD crates from leadership. This task is free to run, and can be donated to fulfill the Gems requirements of the coffer.