With your original character, raising levels will be tough until they release the next chapter, but @caleb_Larkmagnet1 is right, filling up the great engines is the fastest way to level up. Another one that helps make progress at low levels is using aether to clear the fog in the street lamps. And, of course, fighting.
As you've seen, the automatons have a lot of new resistances and vulnerabilities, to match all the new abilities our characters get. Sadly, you'll have to raise a few levels before any of the wrist weapons or hammers will work for you, but the basic dueling cane works well against almost all the early enemies. If you are good with the sniper rifle, piercing is amazing against Bombardiers (but not so well against Pacifiers). Technomites resist fire and cold. Troubleshooters resist water, but take a little more damage from electricity. And water for Combustonauts, of course. You can do it!
