Water and Arcane?
The lack of universal viability in Fire/Earth/most of Air magic traitlines means that you will eventually switch your traits to mostly Arcana/Water anyway, so you’re really already going in the right direction assuming eles don’t get their bad traits buffed. The optimal PvE build is usually 10 Air magic, 30 Water Magic, and 30 Arcana, from what I understand.
I think scepter/dagger is probably your most useful set in PvE. It has the ability to apply the Might boon in very large amounts to yourself and your nearby allies with its myriad combo finishers and quickly recharging fire field. It also has the two fastest healing skills eles have on their weapon set skills, being Water Trident and Cleansing Wave.
Anything goes for PvE.
I’d strongly suggest not going Water and Arcane for PvE because they’re not about damage. They’re one of the best for PvP (and WvW skirmishes), but for PvE damage is what it’s all about, so you’d be better off with Fire or Air.
As you level up, you’ll figure what works best for situations, just don’t be locked in a mentality of “I must use X because everyone says so”, try it for yourself.
As for weapons, D/D is good if you like playing sorta melee, there’s plenty of combos and you press a bunch of buttons (button mashing) all the time so I find it really fun.
Since you’re playing melee it’s good if you can spare a few points for survivability/defense, since you’re more likely to take hits unless you’re really experienced.
I leveled with a Staff from 1~80 and I found it to be best for me, since I enjoy taking lots of mobs at once (it gets great once you have Glyph of Storms).
As much as I’ve tried playing a Scepter, I couldn’t get it to be as efficient as D/D or Staff, so I only used it on groups for the boons (really easy to get combos off) and avoided it solo.
So try them out and see which playstyle you like best, I think both D/D and Staff are good for leveling (though I think the Staff’s better in various situations), and the Scepter… if you can make it work for you, that’s good too.
I really don’t recommend arcane imo. Either Water/Earth for defense or Fire/Air for offense. Arcane has alot of drawbacks compared to elemental skills.
Here is a short guide about the elementalist traits:
Arcana/Water has the highest survivability and still nice damage output. Especially Bountiful Power and the additional Boon Duration help a lot when it comes to DPS!
There is no best weapon. Staff has nice AoE and CC, scepter has good damage and can stack Might easily and D/D is mainly used for mobility and defense (although it can be used for damage as well). Every weapon is good for PvE but for PvP I would recommend D/D or S/D. Staff is not that great for PvP.
I hope this helps.