So are these quests not playable without side quests because I don't have any as I didn't buy the Harad cycle or Lost Realm cycle? Should I look to buy something else first?

You should be able to beat them without side-quests. They're just good choices strategically.

You'll be fine without Side Quests. I was able to beat each of these quests using just a Core Set + Wilds of Rhovannion for my blog:

https://darklingdoor.wordpress.com/path-less-traveled/

The player cards that come with Wilds are pretty powerful.