Out of Cooking, Scribing and Alchemy what should i focus?

Levelling up my professions whilst i play, I kinda want to lighten the load and only focus on 1 of the 3 as they all kinda serve the same purpose, i know alchemy has short but strong buffs, scribing has weaker buffs but has an aoe and cooking has weak buffs but for a longer duration but idk what to do

btw im a mage and i want to be incorporating heal into my builds in case that helps

 

It's generally not recommended to level up professions during a first playthrough due to how grindy they are, but if you insist, here's some information about each:

Alchemy: It's really useful endgame on classes with low healing, since crafted healing potions are much better than the normal healing potions.
Scribing: Good for grind parties, due to the AoE effect, and also good for applying strong buffs that'll last the duration of most bossfights. (depends on the boss, and the scroll recipe)
Cooking: Great for general gameplay, since food lasts a long time. This means that a single batch of food can last hours, if not days, and allows for a much more casual experience.