G'day Loch-o, mate! How tha bloody hell are ya?
Well, free ebooks? A good place to start is right here at Mobileread:
https://www.mobileread.com/forums/ebooks.php?
These are all public domain or creative commons books, and so on - nothing illegal (by regional definition...but you will see what I mean in the copyright blurb if you look at any of them).
Other than that, the wiki has quite a few links to free ebooks:
https://wiki.mobileread.com/wiki/Free_eBooks
As for what's worth shelling out for, I'd say, with the Iliad, a decent dictionary is worthwhile. There's a freebie here, but I don't always find it gets the words when I do a lookup, whereas the big Chambers dictionary, or the Oxford Concise, are often recommended here. I'm yet to buy one myself, but I'll be getting the Chambers.
Anything else requires an answer to the questions, "What's your poison?"
Cheers,
Marc