Most people would not say "I don't have any job" - even though the grammar is okay. "I don't have a job at the moment, and I'm eating up my reserve." sounds good. You could also say "eating into my reserve" or "using up my reserve" - any of those sound like natural speech.

I don't have any job at the moment and I am eating up my reserve. OR I don't have any job at the moment and I am draining my reserve. OR I don't have any job at the moment and I am using money from my reserve.