fish can survive a "fish-in cycle". It's just not recommended or deemed fair to put the fish through the stress of it. That goldfish of your friends is probably quite a tough fish however I imagine surviving the fish-in cycle has taken a few years off its life.
Many people on here (a majority) will say that the bottled bacteria is useless and possibly even a scam(!)
There used to be bottled bacteria that had to be kept refrigerated and had a short shelf life (best before date or whatever) that seemed to help cycling a tank.
The stuff that sits on a shelf for god knows how long, logically, you wouldn't think the bacteria could still be alive(?) to actually do anything.
All you want to be adding is a good de-chlor to your water. Some de-chlors also have stuff in that promotes the natural slime coat of the fish. My tip is to buy either a pond de-chlor (lasts longer!) or get Seachem Prime

(which is good stuff)
About the fish youre thinkin of getting. I'm not going to make a suggestion, I reckon you'll make your mind up when you get to your fish store

Another thing I'd say is that if theres nothing at the fish store that you really want.. then don't buy something for the sake of it! You really are committing when buying fish, I have a few regrets about fish that I have bought in the past
Anyway, good luck and hope to see some pics of your tank on here soon!
