If you're looking just for offense, marksmanship and/or skirmishing is the way to go. Looking at the traits, it doesn't really seem like anything too spectacular opens up until you can get to the level 40+ traits. Try just speccing for stats for now.
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Early on, I would actually invest in the Beastmastery 10-point trait to raise your pet's attribute bonus every time you get a kill, then focus on keeping them alive. If you stink at that, you still get two seconds of quickness on switching 'em out.
Once you hit 80, though, you're going to AT LEAST want to invest in twenty points in the Marksmanship (that's the power tree, right?) tree. It has three essentially tier 2 traits that you're unfortunately going to have to cycle between - Piercing Arrows (great for Short and Longbow), Spotter (decent for parties) and Longbow/Harpoon Gun range increase (gets the max damage possible out of Longbows and is sort of necessary for WvW.)
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If you are offense minded, sword/warhorn is so much stronger than short bow let alone long bow it's not even funny.
Arrow piercing sounds great on paper, but in practice unless you are in WvW chances are it takes more effort to line mobs up properly than to just slaughter them with sword or axe aoe.
People don't get that the 5 points in beast mastery is best used with melee weapons. Because if you swap a pet, your pet has to run ALL the way back into melee range and most likely doesn't benefit from the quickness buff at all.
With sword you can allow a jaguar to take full advantage of those 2 seconds of quickness and pop it's F2 right away, meaning you get far more damage from the stealth crits than possible with ranged.
It also works well with Rampage as One, and can be chained after with QZ for 6 entire seconds of quickness, exact same number as the Jaguar's stealth duration while your Rampage + sword gets your Jaguar 25 might stacks by the end of it.
The easiest traits to use are beastmaster. Because pre 80 your pets will almost always scale better than your gear provided you use the right pets (Jaguar + River/Marsh Drake), you will be one of the classes capable of leveling at the same speed as a warrior without a care for safety. Getting the pet crits -> heal in the skirmishing tree will basically make your jaguar tank like a bear while F2 is up.
Also with this trait set up, you don't have to give a flying !@#$ what items you use. I only said sword because you wanted to be offense oriented, but it works basically with everything giving maximum flexibility while leveling. You are more limited by your gear than you would your traits then, and can swap weapons when you find it boring without having to go retrain.