Question about investing in retirement programs.

I am 25, make about $55k and have multiple jobs. My primary job is teaching (40k) and do coaching on the side for the remainder. As a young teacher, what is the best option of plan to invest in - 401k, Roth, etc.?

My other question is what happens if my career changes? I do not plan on teaching but for only a few years. Do I set this plan up at a bank, an investor or with my employer?

Thanks for any help and I apologize for so many questions. I am brand new to this and am wanting to make the best decision longterm and there just seems to be so many ideas out there on what is best.