First, job combinations are the teams of characters you want to use. How you make your team and what job you select will represent your playing style in game. The following are just recommendations, not Rules.
Its highly recommended to start with a scout in your team, the scout can heal automatically, and without the need of potions.
Fighter - Elementalist - Scout
The most basic setup. With this, you'll have a tanker (fighter) which receives and endures the damages from enemies and effectively lure mobs with the fighter's innate skill Provoke, and a nuker (elementalist) that clears the mobs effectively with his/her AOEs. And of course your scout is there to buff and heal the tanker and keep the team alive. A very versatile team if you ask me.
Fighter - Musketeer - Scout
Just like the first team, you'll have a tanker and a killer. This group may not be able to lure as many mobs as the fist team since this group relies more on "fast-kill" because the musketeer's AOE's aren't as great as the elementalist's. But a musketeer damages stronger than elementalists in terms of skills and normal attacks. This is a good team against bosses or 1vs1 situations and is more of PvP oriented.
Fighter - Wizard - Scout
A good team that has a tanker and a decent nuker. Plus, with this team, you can even make your tanker more effective with the buffs of your wizard. This team kind of lack in power compared to other teams with a fighter.
Musketeer - Elementalist - Scout
A strong team for mobbing since you can kill mobs really fast with the elementalist's AOE's and the musketeer's attack power. But be cautious since this team lacks on defense.
Musketeer - Wizard - Scout
An alternative team for decent mobbing and 1vs1 situations. Utilizes the wizard's AOEs for your mobbing needs and the musketeer assists in clearing the mobs left since wizard's AOEs are not as great as the elementalist's. And as for 1vs1, the wizard assists the musketeer.
Wizard - Elementalist - Scout
The magician team. This team offers more AOEs and different setups for mob control -- be it offensive or defensive through the wizards buffs and curses. Be weary that this team lack on HP, so you need to watch out for those ultimate skills during PvP if you don't want to die with just 1 hit/skill.
Fighter - Fighter - Scout
With this team, you can endure and engage on mobs few levels higher than you because of your fighters' high HP and defense. But you may have trouble fighting flying enemies.
Musketeer - Musketeer - Scout
Love guns? Then this team is for you! This setup kills opponents faster than they can even get close to hit you. This team offers a really high attack power. But must provide range in order to be effective. Musketeers aren't really good in close combats. They need a certain range to use their skills.
Elementalist - Elementalist - Scout
Make this team if you really love AOEs. This team kills bunch of mobs really fast and you may have the privilege of having different elemental damage at the same time. This team lacks on HP and defense, so be careful.
Wizard - Wizard - Scout
This team doubles the effectiveness of wizard's AOEs since you have two of them. But the real benefit here is that you can hardly die in dungeons with mostly melee-type mobs because of their Levitation stance and run through maps safer because of invisibility skill (Invisible Stalker). But PvP wise, Birdfall from musketeers can easily take down your flying wizards.
Note: This guide was taken from the official forum, it was made by Oeil