This is the build I am using, Ornery Biscuit. Just note, people think that Ines is broken atm due to her passive damage skill, Dark Current not being affected by enemy defense like it should be. So I imagine this build might be nuked later this week.
The build is centered around using Plasma Bullet for the red mod, Current Bonding for the Trigger mod, and the Hammer & Anvil shotgun.
Plasma Bullet will work with a Gun or Sword, but Gun is better. It changes her #1 into a Toggle that allows bullets to act as her normal #1, which will place the Conductor debuff on mobs, and to trigger her passive Dark Current. It also changes her #3 from a super nuke into a forward Dash that reloads the gun and generates special resource. It has 3 charges and a very short cooldown. She is very fast in this build.
The Trigger mod will only work vs. Bosses, Tyrants and Commanders, so its really only needed for higher end content like Colossi, Axion Plains, Breach and Bounties, but I use it all the time. To enable the "bond" between you and the target, you'll need to use her #2 to hit the mob. You'll see a current connect you and the mob, this will allow each bullet that hits to dea increasing damage based on the stacks of the bond on the mob. For a Skill based build, this will enable her #3 to hit much much harder at full stacks.
Some explanation about the gun, Hammer & Anvil. It has two fire modes, "Hammer" which fires out slugs, and "Anvil" which fires out slugs that air burst and send out tracking bullets. This build wants to use Anvil. The default mode is Hammer (square reticle), so after every zone you'll need to switch to Anvil (circle reticle). The number of tracking bullets is relative to the number of shells in the magazine, I've seen 50 on Ines. Each of those tracking bullets will count as an attack for her #1 skill, which will hit for 2m each. So when you're fighting, you'll want avoid actually shooting enemies so the slugs will air burst and send out those tracking bullets.
Combat loop is simple. Switch to Anvil mode via ADS, toggle her #1 and start shooting above mobs. Use her #3 to reload and/or movement. Use her #2 on bosses to enable Bonding, if needed, and general burst damage. Use her #4 more huge AoE damage. Takes a bit to get used too, there are times when I use her #1 by mistake due to muscle memory so it toggles the skill off, and not shooting at mobs to hit them is odd.
I honestly don't see this lasting. The Dark Current damage is really good, but its not being reduced via enemy Defense, plus using her #1 isn't using enough mana. I think they intended for this to be an ebb and flow type combat loop, where you get high damage via Gun until mana is gone, then go back to Skill damage to allow Dark Current to regen mana. Hopefully all they do is enable Dark Current to be affected by enemy Defense, but not too harshly.
Edit: Also, don't use the Bravery set like she does, unless you're really good at movement tech. You become a true glass cannon. In the above build, I swap out HP Conversion (MP) for Increased HP, and I use 2 piece Circulation / 2 piece Plague. Could also use 4 piece Slayer.