How do I get my lvl 100 Legendary Item? The easiest method is to get your LI crafted. The first mat is Blemished Symbol of the Elder King. The symbol drops from lvl 90 boxes, in any Big Battle if you reached lvl 100, and also it is a Quest Reward in Central Gondor when you finished everything (including kindred reputation with all factions). Second mat is 2 emerald shards that you can get from gathering crafting mats - rare drop, buy it from skirm camp or barter in Helm's Deep. Third mat will be 5 of the highest crafted mat of T9 wood/ingot/leather/parchment. You can also do Roving Threats and barter your LI.
Now that you have your FA LI, you must get the legacies you want. Collect all the lvl 100 3rd age LIs that drops from kills, farm the IXP on it or use an IXP rune, and when it reaches lvl 30, you may deconstruct it by chosing the legacy you want to keep for your FA LI.
If you play more roles on your class, decide first by wich trait line you are setting up your LI. Pure dps? Healing? Tanking? Hybrid LIs are not the best ones, in my opinion. Exception always exists of course, for example hunter, there are simply not enough legacies to fill up for a single trait tree.
Things you must do before imbuement: Use Anfalas Scroll of Delving - it will add +10 levels. Spend all points (they reset by reforging and using empowerment scrolls). As I wrote above, have the right legacies. Advanced option: Use an Anfalas Crystal of Remembrance - you get one from epic, if you can afford buying them.
Recommended, howewer not necessary to - max out your legacies before imbue, - use the 3 anfalas star-lit crystals before imbue. What will I need after imbuement? 10 anfalas scrolls of empowerment per legacy. 9 anfalas star-lit crystals (if you used 3 before) per LI. Tip: if you make a tank or healer LI, you do not want to max out your dps with star-lit crystals, since your point is not dpsing when you use that LI.
How do I farm all the empowerment scrolls? There are dailies you can do for it, 4 per character comes as minimum, howewer for that you must own Western Gondor and Old Anórien quest packs. Daily 1: Do the training at Beriadur in Dol Amroth. Takes 10 mins for Armoury, once you learn your way around (easiest). Daily 2: Do the South Gate (Smith's) daily in Minas Tirith. Quest giver: Narnaith at the Main Gate. Daily 3: You may also do the Burgsmen daily at the same place but it is more time consuming - doesn't pay off on the long run. Join a marks&meds farm - Thorog (must have Misty Mountains quest pack and completed all Helegrod Wings to be able to enter), Sambrog (must have it also unlocked by doing all the Great Barrow instances), Ost Elendil (should own Evendim quest pack), and the list is endless... Do Big Battles and barter the scrolls for merits (should own Helm's Deep expansion).