Don’t listen to anyone who suggests learning the London. Better to learn opening principles than a system. If you want to learn one, I recommend Italian, because it lets you castle early, and then you can just play principles. Don’t do a bunch of boring memorization. It won’t be worth it.
Suggest an opening I should play to push till 600. I do think that it's definitely achievable, I just need to improve my theory and technique.
Suggest some openings I can try or anything that you would like to advice for how to learn theory correctly .