A simple to use table for calculating required skill points from one tech to another for all major skills can be found here: Aero's Skill Point Calculator Courtesy of Admiral Lunarion of Aero
Most of these skills determine the maximum tech level of various types of gear that you can use, these cannot be reset.
Advanced Class Subskills require Advanced Skill Points, which you can get by training your class skills above level 20 in Lyceum. Each subskill costs 1 Advanced Skill Point.
These skills need 78 Gold Bars and 9 Platinum Bars total to train.
These are mission based skills found in Free Market. You can only train in 1 trade skill tree per character.
Trained in Lagrange
Also trained in Lagrange