You will earn "Rugby Dollars" for most things you do in the game Tutorials, Matches and Career mode.
This will take a bit of grinding out, but I would leave it until you have completed everything else so that you know exactly how much you need.
After you have simulated your career ($17,000) and all the Tutorials ($45,000) and played and won 10 matches ($5,000) you should have around ($77,000).
To grind the last $23,000 you can either play another 46 games or simulate through another career and a little bit, which is quicker than playing.
One small tip here is when doing the tutorials if you earn silver medal, then retry and get gold you will earn more Dollars.