Check the gathering books before choosing a starter-quest reward. Mining for Dummies, Wild Harvest and Pelt Collecting for Beginners teach Mining, Herbalism and Skinning respectively when used from your bags. For an existing skill, they add two points but cannot raise it above 15.
The Mining, Herbalism and Skinning tooltips retain the two-primary-profession limit. A book cannot grant a third profession.
Look at your starting quests
Icy Veins identifies Rascally Rodents in Northshire, Galgar’s Cactus Apple Surprise in the Valley of Trials and the second Coldridge Valley mail delivery as examples. Inspect the live reward choices before selecting a book.
Cagen's testing dates to the October 14 beta; this site has not repeated those quests in the live game. Mining and Skinning also need their tools, so check a vendor for a Mining Pick or Skinning Knife.