Successfully complete all the Mage Guild Recommendation Quests to gain access to Arcane University. Then, create a Fortify Skill 100 spell that lasts for a few seconds on-self for Mercantile and/or Armorer. With the Mercantile spell, cast it in front of a merchant, activate them, and you will be able to invest 500 gold at their store without being a Master in Mercantile. In addition, you can drive harder bargains. For Armorer, cast the spell and then equip an Armorer's Hammer. Your hammer can be used infinitely without being a Master Armorer. You cannot, however, repair magical items without having legitimately reached the Journeyman Armorer level. Similar spells can be created for other attributes and/or skills: Personality and Speechcraft for raising people's dispositions, Security for picking any lock, etc.