This Achievement is unlocked by getting 10 skills to Level 1. After you start the game, you will talk to Emily on the Wharf after your vision, and you will get to choose your field of study (it doesn't matter which of the three you choose between Diplomat, Detective, and Occultist). Once you pick one, all 5 skills in that "tree" will become Level 1 and that's 5 out of 10 right away. You will notice you have points you can put into your skills to level them up. It takes 3 points to get a skill to Level 1 (be sure not to put points into your field of study Level 1's!) Then hold the X? (forgot the button, it shows on screen though) button to Validate your choice and make your point usage final. At the end of a Quest you will receive 4 points to put towards your skills. So it'll go like this if you follow my lead:
5 skills at Level 1 initially
Quest 1 Complete, 3 points to Skill "A" to make 6 skills and one point to Skill "B"
Quest 2 Complete, 3 points to Skill "C" to make 7 skills and one point to Skill "B"
Quest 3 Complete, 3 points to Skill "D" to make 8 skills and one point to Skill "B" to make 9 skills.
Quest 4 Complete, 3 points to Skill "E" to make 10 skills and unlock the Achievement.
You can also upgrade your skills by using them in conversations along the way, but doing so will likely use up Effort Points so make sure to use any Royal Honey you find to refill your points. Though as I've shown above, you can get 10 skills to Level 1 without worrying about this at all, as long as you know what to say, your skills are honestly pointless.