Welcome to the forum, Dark
Strider!
If you have not read
The Silmarillion yet, I'd suggest starting there. Most of the HoME deals with it, giving the evolution of
Tolkien's
First Age legends...from the origin of
The Silmarillion in 1915 or so, on through the rest of his life really, and some related essays... for example Tolkien's very late writings about
Glorfindel. There are also some HoME
books that show the evolution of LotR.
If you have read
The Silmarillion, then you could start with HoME 1 and 2, the earliest of his writings found in HoME, and read your way through from there.
If you want some specific information right now, or like a specific tale, post it here and we can tell you where to find it.
Always a great read is The
Fall of Gondolin in HoME 2, especially if you like battle. A lot of people really enjoy parts of HOME 10 that deal with
Morgoth and
Sauron, as well as Tolkien questioning some things such as the origin of
orcs and the long standing myth of the making of the Sun and Moon.
If you have special interest in
Numenor right now, you may want to read parts of HoME 5... to discover the origin of that tale. There is also a later version of the Fall of
Numenore in HoME 9. If that stuff interests you,especially the time
travel story, you may want to read the Notion Club Papers, and I can tell you more about that if you are interested.
If you look around the HoME forum here, and especially visit the Sticky thread "Of Reading UT and HoME" you will get a lot of information about HoME.
PS: If you have not read
The Silmarillion, you might want to check out portions of
Unfinsihed Tales if you have it, because some sections deal with LotR topics, and reading those chapters will allow you to get a feel for the way Christopher Tolkien presents his father's writings... his introductions, commentary and the notes he gives.