Be wary of gladiators outside the colosseum. They don't take photos for free and can be quite agressive about their payment. Also don't be fooled into taking an unlicensed guided tour of the Colosseum either....
I'm a Bondi local...it is always packed with people...if you're looking for a more chilled beach hang out, check out Tamarama, Coogee or Bronte beach, all 5-10mins from Bondi.
My best advice is to step outside your comfort zone and make an effort to talk to EVERYONE on tour. I made friends from 6 continents on the one tour!!!