EDIT: You're not in Melb, ignore this paragraph!
I'm not sure if you already know this, but MJ Bale are opening up in Melb in flinders lane in Nov.
Also if you're in Melb, check out Tolley in Bourke street. They are just down from American tailors, and they have a good range of suits. Although their range of 36 chest suits are small/non-existent, but they can get them in. They offer a MTM service as well, which is about $1000 from memory. Frankly though, I'd stick to off the rack in the beginning, until you know what you want.
I've got a suit from SuitSupply and it's great, but I was in a position to order different sizes and return the ones that didn't fit. This probably isn't the best option, especially in the beginning. Stick to MJ Bale, especially as you're a sydneysider!
As someone else who is starting to enter the world of better dressing, I'd say start slow.
Also for the shirts, check out MJ Bale's 5 for $240. Good selection of CBD-appropriate shirts in there.