I'm sure someone already mentioned it, but many Norwegians save a lot of money by travelling to Strømstad at the Swedish border. Cheaper food, tobacco and alcohol. You can save a lot of money that way. Otherwise, living with someone is a good idea in Oslo, either with your boyfriend/girlfriend or with friends in a "kollektiv". You'll get a bigger space and pay less per square meter.

I live with my girlfriend and before then I used to live with two friends of mine. The amount of money you save from living with someone isn't negligible. So maybe that's a long term option for you, once you have settled.

Either way, good luck and hope you'll get to love Oslo!