I love this game and I suspect you will, too. You can play a long time without expansions using the links above. I found playing solo with the core set was very rewarding. There are also a dozen or more custom scenarios out there using only core set cards. The following three decks are strong core set only decks, too:
http://boardgamegeek.com/thread/898293/journey-down-anduin-deck-built-only-single-core-set
http://boardgamegeek.com/article/9763507#9763507
Edited by Strategian