If you have the money to get all that stuff right now (cycling bibs, cycling jersey, clipless pedals, and cycling shoes), I vote for just getting it now. That stuff is way more comfortable, IMHO, so why not just start out comfortable? If you can't swing it right away, I vote for the pedals and shoes first, but that's just my preference. I can ride in regular clothes, but I much prefer to clip in. Even though I bought dual-purpose pedals (platform one side, clipless the other side) for my ultra-beater/commuter, I almost never ride the platforms on it because I don't like the feel underfoot compared to being clipped in.

Good luck and enjoy it!