There have been some changes to the rules since the Moria boxset. That said, no reason not to play with those rules if you are just running a game for you and a buddy. If you would like to play against others, you will at minimum need the most up-to-date rulebook, which is the "The Hobbit: Unexpected Journey" hardcover. (Distinguish this from the "The Hobbit: Motion Picture Trilogy™ There And Back Again" hardcover.) Next, depending on what army (or armies) you want to run there are five "Lord of the Rings" army books: , Fallen Realms, Free Peoples, Kingdoms of Men, Mordor, and Moria & Angmar. Finally, you will need some figures. Each army is made up of warbands led by a hero and, in most cases, a retinue up to twelve warriors. So you don't need very many figures, especially to start although you will probably take at least two or three warbands.
Battle Companies requires even less figures. You are basically running a single warband in a series of connected games where your warriors will gain experience, become heroes, or maybe just die trying. It's really fun.
HUGE CAVEAT: The rules will be updated again this year and there will be a new hardcover rulebook rebranding the whole line as "Middle-earth Strategy Battle Game." (You can already see this brand change on the cover of the Battle Companies book.) For that reason, I would suggest not buying the Hobbit hardcovers at this time. We don't know exactly when the new book will come out but it is supposed to be in 2018. If you want to get started before then, maybe consider finding a used rulebook on ebay or maybe even getting the Escape from Goblin Town set.