Will leave it to Pro4Never to link you to the references about skills and classes, however as for recommendation it depends really on what you want your end class or play style to be. Once you know your end class there are some favorable paths that people tend to go for example if you want to end Trojan most people tend to go Water-Warrior-Trojan. Warrior is a very common middle rebirth class because of how strong the skill "Reflect" is which is a random chance to negate incoming damage. To sum it up for you
Trojans - are high dps beserkers
Warriors - are sort of like bruisers (decent damage, but more tanky then trojans)
Archers - are utility based (stun locking / cc)
Water Taoists - are utility / support mages
Fire Taoists - are ranged mages with a consistent damage out put
To add onto this, Heroes introduces 2 new classes, monks and ninjas. It also introduces new 'pure skills' for players who want to stick with the same class and adds the reincarnation system so players can re-work their previous lives.
MonksPrimary Uses
-Interrupting agile enemies (lower damage but slight stun allowing for combos or allies to help)
-Cleansing negative effects from allies (remove poison, shackle, etc)
-Buffing allies (elemental resistance, bonus crit chance)
-Pure skill (soul shackle) locks down enemy ghosts making them unable to be revived or move
NinjasPrimary Uses
-Cursing enemies with poisons (reducing hp over time, blocking healing, knocking down flying targets)
-Focuses on picking off low health or low defense targets (weak vs tanks)
-Pure skill (counter-kill) randomly teleports behind someone who attacked you dealing damage and then returning you to your initial location.