The One Ring is hands down the best middle-earth
rpg in existence, and their campaign books The darkening of mirkwood, the heart of the wild and Rivendell all give you more campaign leads than you can realistically handle in your gaming life. So I suggest to invest some money and save yourself a lot of time, while still having the freedom to build the adventures yourself.
It is really well worth the price.

Of course they also have complete adventure books.
Other than that, the classic Merp supplements are easily found online, even though they are technically still protected material.