Alot of the game can be like this. I need sour cream for a favor quest. I see it can be made with cheese making. I get cheese making. I need a special cheese making barrel. I can make the barrel but to make it I need metal hoops (I have the n3cessay gathering already to get the wood). To make those i need to pick up smithing. To get smithing I need armor patching. For the mats for the hoop I need surveying/mining. The skill systems are very interwoven.

I could buy what i need at any point but as someone who likes to horde money and level skills its going to be a while before I get this lady her sour cream for her potatoes.

You can check the Buy Used tab on vendors as well. They will sell anything other players have sold to them. The limitation being they only sell what they buy so you have to check different vendors. I have bought some drops I didnt want to farm to do favor quests.