The best offense is oftentimes a good defense. As a Knight, your defense is near-legendary, and many of your Misc. Skills will only further your survivability on the field of battle.

Almost forgot some of the most important skills! They are technically weapon skills, but as you can't actually use them to deal damage, I'll put them here. These are your Knuckle Masteries. They affect your hit accuracy. All three of them (Unconfirmed, as the second one is supposed to be a damage increase). The first one (and supposedly the second one) increase your accuracy by 10% when mastered, and the third one by 20% when mastered.

Stamina Upgrade: Available at Level 5, Upgradeable 10 levels. For each skill point you put in this, your Stamina will rise by 3%. So overall, this is a Stamina boost of 30%. Seeing as Stamina is one of your most important stats, and that this is the only one of two Misc. Skills you have available at the beginning, I would recommend starting on this somewhat early.

Iron Armor: Available at Level 10, Upgradeable 10 levels, Requires Stamina Upgrade Lv.10. For each skill point that you put into this, your Physical Defense will rise by 3%. So, overall, this is a Defense boost of 30%. In addition to the previous Stamina boost, the fully mastered Iron Armor skill will make it a lot harder for you to get  Latale Ely  injured in combat. Your defense should already be quite high from the Stamina Upgrade, so you can ignore this skill until you level higher, but more defensively-minded players will want to add this earlier.

Magic Armor: Available at Level 20, Upgradeable 10 levels, Requires Iron Armor Lv.10. For each skill point that you put into this, your Magic Resistance for all elements will rise by 3%. So, overall, this is a Magic Resistance boost of 30%. If you tend to fight bosses or magic-wielding enemies in PvP a lot, you might want to invest some points into this skill. Otherwise, you can ignore it until higher levels / entirely. Comes in handy around level 70-75-ish, when you start fighting enemies in Ktuka Ruins, or Javawalks.

Pain Relief: Available at Level 40, Upgradeable 10 levels, Requires Magic Armor Lv.10. For the first skill point that you put into this, you will be given a 1/10 chance of recovering 10 HP if you are hit by a Physical attack, and a 1/10 chance of recovering 10 MP if you are hit by a Magical attack. For every skill point invested into this skill after that, the rate of HP / SP increase will increase by 3 HP / 2 SP. So, with a Mastered Pain Relief skill, you will have a 1/10 chance of recovering 40 HP / 30 SP, depending on what type of attack you are hit by. IMO, this skill is pretty much useless. I could see this skill being useful from level 1-25, when a 10-40 increase in HP would actually amount to something. Don't get  Latale Ely this skill.