Well, Dougal sells most common healer potions, but he doesn't sell any food. You can also find two quests scrolls he sells. One to use for a part of G1 and another just to earn some extra money

He doesn't sell base potion though and his prices are pretty much the same as the prices at Healer's place. You can go back and forth between TNN as long as you use the Black Fomor Pass on Saturday as often as you like, even after you finish G1. There are no herbs in Albey to pick...well, maybe in normal, but not the G1-related dungeons. Hope that helps

You should also bring some spare weapons if you want to stay there for a long while.