It depends on what you want the character to do.
Fastest farm build(Highest gold per 24 hours). This build is all about fast killing to maximize gold per 24 hours. I have over 10 gold farming builds, this build surpasses them by about 15-20mil gold per day.
Axe(Pummel), reserve, assault, shield, Enhance.
Boss camping. This build combines curse and assault for instant cast everything, and high damage from mana overflow and all the spells that combo to instant kill a boss.
Chaos, Life, Curse, assault, Staff hit.
Healer- This build focuses around buffing a main account and keeping it alive, as well as supplying damage buffs to help kill faster.
Life, earth(or chaos if your main is earth,wraith), curse, spear(Senki support), assault.
Bow is decent for pvp, but sub par at end game content, their number 1 damaging spell is steel rain, which has a 5 second cd and is for under lvl 200. Bows training skill(Rapid Fire) has a 4 second cooldown. Which is bad for training because that means you can only kill 1 mob every 4 seconds. Which is very slow.
Spear is good for pve, but really lackluster in pvp. All the good spear skills require targeting unlike axe, chaos. which is harder to do than it used to be, and they do not hit for as much as the other classes. It shines in pve because of all the defensive debuffs it puts on mobs to make you kill them faster.
Axe is top contender right now due to holy pummel with is an area target skill, that has a very low cooldown, that also stuns and multihits. It has everything you would want in a skill, with 0 downside.
Shadowblade is good for pvp, bad for pve. Its training is tough because it has no defensive spells, and uses mantle. Which makes it a glass cannon. The main reason shadowblade is taken is for the buff "mad enhancement" which gives you a ridiculous amount of stats.
Chaos has a buff that has a chance to proc extra damage(The proc hits for more than any other skill you have), on top of that chaos has swiftness, and the new skill that does swiftness and thunder fury at the same time. Top mage skill right now. Best for aoe training.
Life is used for the buffs. The attack skills are lackluster.
Wraith a needed skill to train as a mage. Forbidden curse recovers a ton of hp and mana to caster when it hits. You will not be able to train without it.
Earth- The only other skill that can self sustain without wraith is gnash. When it kills a target it recovers mana and hp. In my testing if you cannot 2 hit gnash a mob, you will not be able to sustain. Earth has a bunch of SD debuffs from spells and is in my opinion very sub par.