The Merchant Airship is a good source of speed ups and resource packs.
When it is unlocked, it will appear at your Airship Dock 2-3 times a day.
You will be able to exchange resources and materials for resource packs and speed ups.
This is really good way of trading as you can pick up more resources than you trade in.
For example you may trade 5mill food for 4x2mil food packs.
Be sure to check it out and note the timer so you can check back when new airship arrives.
This ship will be located at the Airship Dock when unlocked, which is on the west side
inside your castle next to the Arcane Sanctum.