How does importing work?

Hi, I'm new and I want to sell stuff on ebay and blujay so I'm planning to buy wholesale or liquidated stocks.

I got a few questions here...

Should I buy wholesales from the website given or contact the sales manager?
and
If I buy from wholesales at their minimum amounts, do I have to inform customs even though it may be just one to three boxes?
and
If I buy a pack from PPWDG, do I have to inform customs or it isn't necessary?
and
Do I have to get taxed for the small amount of products I import? If yes what sort of information must I give to them to be taxed.

I'm really new and I just need basic information on how importing works. I'm afraid I might violate some laws unintentionally.

Pls Help,
THanks.... SC, Australia

Have a read of our Shipping Handbook Link hidden: Login to view which will help to answer some of your questions about importing.