Not sure of Carnegie Caulfield CC junior program - contact then to find out about club bikes and their training program
Carnegie Caulfield Cycling Club
I am a member of Blackburn CC. Through summer we have introduction - beginner training sessions weekday evenings plus racing ever Saturday afternoons. We have a number of club bikes to use for training and racing
Blackburn Cycling Club - Home Page
The Avanti pista would be a good starter bike, as the Hillbrick I already mentioned. No point spending big $$ as you will soon outgrow what you buy. Hard to tell exactly what size you are on as Reid don't display a geomerty chart. Think it may be a 54cm tt. There was recently a 54cm Avanti Pista for $300 on FB, so if you aren't in a rush will find a good bike in your price range.
Main thing to check for when shopping is that the cranks are 144BCD cranks. As over time you will need to buy additional front chainrings and 144BCD is standard.