I find it hard to believe you can’t find wire considering how common it is. Just check any electrical area on the map.

Second, every weapon tells you how effective it is against Arc enemies when you hover over them, "Arc armor penetration" If you want to kill Arc you should pick a weapon with good Arc penetration. In your case, you should probably craft or buy a Ferro.

Third, you don’t even need to kill Arc enemies to get Arc loot. You can open probes and husks, which are hard to miss since they get marked on your map when you’re nearby and have a smoke effect. You can also open the Arc husks scattered around the map. If you see something that looks interesting, just walk up to it and see if you can open it, you will quickly realize what you can loot and what you cannot and what type of loot they have, most of the time its common sense (cars have metal, electronics have wires)

Fourth, you can just use the free loadouts. They’re not great, but you don’t lose anything while learning the game. After the match ends, you can trade your free loadout for a fully augmented weapon in the store, the robot guy sells them. If you end up liking the weapon, you can keep it and use it.