First time round: livebearers (mollies, guppies, platies, swordtails), but I can't remember in what order I bought them. Only a general impression that I must have got too many kinds too quickly.
It was either a fairground goldfish or a wild caught bream from a local river, it was over 25 years ago so I don't remember which came first!
The goldfish lived forever and ended up in a pond where it produced generations of offspring.
The bream was sadly fished out of the tank by my cat.
Who ate him.