The nice thing about the rebirth option is that as a Knight, you can test out certain skills or builds and you can change your build once you rebirth and go high swordsman / lord knight.
If you are a VIT / spear build, pierce is probably your best skill for single targets as a knight. Clashing Spiral will take its place as a Lord Knight.
If you are leveling by mobbing and AOE mostly (which is recommended, or else it's slow), make sure your main AOE skill is maxed. So make sure you max either bowling bash or brandish spear, or both if you plan on chaining the two. If you are using spears for the AOE, max spear mastery for more damage too. If you have points left, then you can use it on Pierce so you have a good single target damage. Spear boomerang comes last in this case, as it's a long range "finisher" type of attack I guess.
If you are short on funds / supplies and are mostly leveling by killing one monster at a time, then make sure Pierce is maxed for dealing single target damage.
Your build will be different as a Lord Knight since it will be somewhat dependent on what Rune Knight build you are targeting if you are not going to reset.
Take a look at the guides on the stickied thread; they are very comprehensive -->
http://forums.warppo...t-build-guides/