Yes, yes, yes. A thousand times yes. Always keep the appropriate level gathering items on you, with spares in your bag. Gather everything you come across as you travel. You can either store it in your materials bank, sell it, or do it the hybrid way like I do; keep collecting until you have a stack in the bank (250 of an item) then start selling. You will be amazed how quickly it starts to translate into a decent amount of gold.
Walking past resource nodes is like walking past free gold.