For medication, once you're prescribed, use a discount program. There are several in your country, but I've found (at least based on their advertised prices) SingleCare to be generally less expensive.

For comparison:
Generic adderall looks to be around $35 US.
Generic vyvanse looks to be around $120 US.

I also found GoodRX. Generic adderall looks to be about the same as SingleCare.
Vyvanse looks to be less expensive.

Looks like a hit/miss, but nothing says you must use only one.

Good luck!!!

Edit. It is funny to me. SingleCare was less expensive on other drugs I compared, but definitely not so on the two I know are common for ADHD, making my first statement and my last contradictory lol