As others have said, when it comes to rotations and stuff you'll mainly find guides and such for level 60, as before that any rotation you find is going to change the moment you learn a new skill. That said, as you level up I would highly encourage you to play around with new skills when you learn them to figure out the ins and outs of them. A few pointers however...

1: Buffs. These come in several flavors. First off there are persistent buffs, such as Maim for marauder, Heavy Thrust for lancer, Twin Snakes for pugilist, etc. These should generally be kept up 100% of the time. Second are offensive cooldowns. These are generally best stacked together due to them being % bonuses. Third is defensive cooldowns. Using these is more of an art than a science, you want to use at least one during any circumstance where you'll take heavy damage (large pulls of trash mobs, "tankbuster" moves from raid bosses, etc), but you also want to use them often just to give your healer more time to DPS as the cooldowns are pretty low. Also of note, any debuffs that affect a monster's offensive or defensive capabilities (Such as Virus, which lowers a monster's str/dex/int) are essentially the same as player buffs, except they only affect one monster out of a group, but can benefit the whole party.

2: Interrupts. These are the debuffs of stun, silence, and pacify. You'll use these to prevent certain actions by boss monsters... unfortunately, the only way to really tell whether a monster is immune to any of those, and what abilities are affected by which status, is trial and error or reading a guide. If a monster does have a skill you wish to prevent using one of these abilities, it's important to ONLY inflict the status when you wish to interrupt, as they can build up a temporary immunity after three or so uses (they also do this with CC abilities, but not damage/defense debuffs or DoTs). That said, if the monster is NOT one that you need to interrupt a move on, go nuts with using your interrupt as a damage skill (most of them are off the global cooldown)

3: Crowd Control (CC). This includes sleep, heavy, bind, and knockback. These are useful for solo survivability and GODLY in PVP. In most PvE content however, they won't see any use. It's generally preferred to AoE large groups of monsters, and any damage breaks these (except Heavy, but a tank can't utilize that AND keep hate). Heavy DOES have a few niche uses in certain boss fights, but that's the only one.

4: Damage over Time (DoT). These are by far your most damaging moves. They do the listed damage every 3 seconds, so if you take the debuff duration, divide by 3, and multiply by the debuff potency and add the damage the move that applies it does (Only Bio doesn't deal damage outside of the DoT AFAIK), you'll find the total potency of the move. Generally they're always your best option (with the exception of Fracture, which is only good for marauders.) That said, you'll only see that potency if it lasts its full duration, so try to avoid DoTs when the mob is almost dead, or if the DoT has plenty of time left.

5: Area of Effect (AoE). These do insane damage on groups. Much like with DoTs, a little math is required to find the total potency per action. Just take the attack potency, multiply by the number of targets, and you'll find the total (except for Holy and Flare, which have their own weird math shenanigans in the tooltip). Generally, with three or more monsters it's better to use AoE attacks.

If you have any questions about particular skills, feel free to ask! Plenty of folks are happy to help.