Car Pack Help


I’m totally new to Forza and loving it. However this whole car pack thing sounds very complicated to me. I have noticed on the store as well a whole lot of individual car packs for sale. Then there is a VIP Pass and a also the FORZA Motorsport 5 Car pass which seems to be around $40. Can someone help and explain to me what this is all about. I do wish however to have ALL the cars available to me and need advice on how to obtain this. Which pack would be best to buy and where can I find a list of ALL cars available on FORZA.

Thanks - Ihsaan