tl;dr

• Lesion's passive provides attack speed and a 100% Toxin buff which will combine with Volcanic Edge to form Gas
• Magnetic has the highest disposition in this build to proc it more often
• Meele Vortex will pull in enemies on kill if the target had a Magnetic proc
• Condition Overload takes care of the damage as you will proc status effects all the time

Budget Alternatives

• Primed Reach:
  • Reach, only if you have nothing else from this category
  • Spring-Loaded Blade, a little bit better than the above
• Primed Fury:
  • Fury, only if you have nothing else from this category
  • Quickening, better, quickly builds up Combo Counter for Weeping Wounds, quite viable
  • Berserker Fury, not recommended, as you rarely crit
• Opportunity's Reach:
  • Mentor's Legacy, only if you have nothing else from this category
  • Master's Edge, okay, but not even close to Opportunity's Reach
  • Discipline's Merit, actually viable if you wish to proc Tennokai more consistently
  • Condition's Perfection, don't use this. Seriously. Despite what is may look like at first glance, the bonus status chance is miniscule
  • Dreamer's Wrath, also don't use this. While the Tennokai proc chance is nice, the crit damage bonus is wasted here
• Drifting Contact:
  • Body Count, only if you have nothing else from this category
  • Gladiator Rush, don't use this, as you can't really take advantage of the set bonus

This build also invests in a Forma in the Stance slot. This comes down to personal preference, but I like Bleeding Willow as it keeps some forward momentum on light attack spam.