Elemental summoner, blade dancer, dark avenger, sword singer. Cheap, good sustain and mostly dying just from PKs as mobs wont be able to do ****. Kinda, you should invest a few milions to maximize the farming speed but the weapon can be even the D grade they give you at 20 since it get stronger with levels. So eventually you'd need to get a B set + A grade gloves of any kind to make it faster.
My warsmith farms faster than dark avenger in the same gear (D from the 20s), and does not use pots in any catas or necropolises lvl60+. I think the summoned golem and that “warmachine help” skill helps a lot, as it is also applied on golem, when the avenger’s panther is kinda lazy and does not hit targets sometimes (this may be a bug)....