Is Amgrow Bonsai Mix good enough?

Hello everyone,
I have just started my bonsai journey. I bought 4 bonsai starters, including Firethorn, Sweetgum, Cotoneaster and Privet.
Now, I am about to re-pot them into proper bonsai pots. I am quite concerned about the pre-mixed bonsai soil I got from the nursery.
The brand is Amgrow Bonsai Potting Mix. Link: www.amgrow.com.au/product/bonsai-mix/
My question: It states this is an organic soil mix. Even though it is created for bonsai, I'm not sure if this can be used for my plants for best growing result? Should I add anything to it or would you recommend me any good brand in Sydney? Anyone has any experience with this?
P/s: I cannot find any Akadama, Pumice and Lava Rock to mix myself in Sydney, Aus.
Any help would be much appreciated!
Cheers.

Have you come across this:
www.mtsylviadiatomite.com.au/

And I have found some reference to "PET TEAM" baked clay.

Diatomaceous earth is awesome. Can be found as unscented cat litter - AKA kitty-dama. Or in some oil absorbents, like OilDri.
Chicken grit, like granite chips, can be used for aggregate, though it's heavy and doesn't absorb moisture.

Harry Harrington has a great 4-part article on some alternatives. The link is below, and the rest is Aussie-specific
bonsai4me.com/Basics/Basicscatlitter.htm

Tim in Brisbane tells me: Diatomite is mined in Kingaroy near Brisbane by a company named Maidenwell. They bag pure diatomite in various sizes and in raw form. It has been fired to 650° and cleaned for use as a growing medium. The majority of colour is white, tan, browns and the odd red. However, finding it is quite hard! A 40 litre bag costs Aus$20. Maidenwell even contacted a local nursery who then contacted me the next day. SEPTONE Dry-up is an industrial product labeled as diatomite. AVOID THIS. It is not cleaned and contains 60% clay!

Thanks much leatherback and brkirkland22. Would you recommend any mixture ratio or simply 75% cat litter and 25% barks will be good enough? Do I need to add anything else other than cat litter/DE and barks, for example soil?

Cheers
Vinh

The whole idea is that you create a substrate wherewater will flow through. Soil will stop that. Just the grains is enough. Mine also grow in mixtures like that.