The biggest difficulty I have found with Shotshell reloading is securing wads. They have been non-existent in Oz for a few years.
If you have a source I would be keen to know.
The economic side of Shotshell reloading is nowhere as rewarding as metallic reloading, it is worth doing your math first. Most people would just buy shotshells these days for 12gauge, however you also have a 20gauge so maybe they are a good deal more expensive?. The exception is making up slug or buckshot loads if you have a mould. Slugs is the only thing I reload and because my production needs are low I just use a Lee Load-All Jnr.