I've been saving some coins and I'm not sure on what should I spend them.
I use mainly sowrds but I already have avenger and a combuster so I feel voltedge is kinda pointless
The other sword option deals normal damage.
Are the poison needle or the vortex bomb good enough or should I invest on calibrators and trinkets?
If none of the options appeal to you, you can sell calibrators on the AH.
The electron vortex is a slightly more awesome version of the graviton. Hoovering up a bunch of enemies with it, then unleashing a combuster charge on them is a great way to do massive damage; you'll get a minor amount of damage from the bomb itself, a huge amount from the charge attack on the sword, and then both shock and fire damage ticks. The only thing to watch for is that there's a big movement penalty when charging it, so you'll want to be well away from the group you're targeting before you whip it out.
The Voltedge is pretty awesome, and would be a good substitute for your Combuster in fire themed levels (like FSC, or in oiler-infested areas).
The plague needle is kinda meh. There's other threads that go into detail (I don't personally have one) but the general consensus is that it's outclassed by the blitz needle in pretty much every way.
The Triglav is a troika line sword, and thus another red-headed stepchild of the sword group.
The Stagger Storm is fun in lockdown and decent for doing noob-training runs, but not much use otherwise.