selling multiple e-books & bundles?

I’m having a hard time figuring out the best option for my situation.

I’m building a website to sell several e-books. I need the plugin I use to do sevearl things:

— have a shopping cart that can handle several books at once (not buy just one book at a time)

– sell a bundle of titles (for example, 3 related books sold together as a package)

– compatible with PayPal standard

– free or very low cost (I have no budget to speak of)

Do you have any recommendations? This is my first time selling digital items and I’m so confused at the array of options.

Thanks so much for your help and suggestions!
all best,
Denise