The secondhand market for many of the armies is still very good so I would get into that.
Aristocrap, in order to evaluate the lists I suggest that you look at what you can make out of the better value troops types from either: generally it is better to have a good defense (as long as you get it cheaply, ie a shield) and preferably something to make you hit harder eg Lances, two handed weapons, Berserkers, Dunlending rule. Smaller units working flanks can be another way to hit harder. Bow is not so good in WOTR vs high defense troops but can be handy vs Hordes of defense 3 troops. I would give up high defense to be able to hit harder with some units early on. So the likes of Orcs/Goblins with two handed weapon (or even bow, they are cheap) are also a solid choice.
Crossbows are great in this game, and Fallen Realms get a very cheap unit of them. The right artillery can be good also, and the Mordor Siege bow is the best of the bunch. If you take monsters, make them heroes. Cavalry needs to be used carefully due to it's relative vulnerability (effectively only half the 'wounds') and tends to perform best when 'buddied' up with foot units.
Either large units with appropriate hereos (eg Captains, spellcasters) to boost them can work Or you can work together multiple smaller units. I use both approaches. Smaller units tend to work better with high def infantry and cavalry, as the aim is to get the right charges and work flanks and the high def infantry can work in units as small as three coy strong.
There are really multiple play-styles and lists within most factions. Fallen Realms can be done in a number of ways, as can Mordor The 'go to' list for Mordor is a whole lot of Morranan Orcs (eg high def for low costs AND hit slightly harder) plus Gothmog and Wraiths. On that view, Easterlings are only a lesser version of the same (eg the infantry costs more). Both armies can have all of the better heroes to boost them up, due to the allies rules. However, there is much more flexibility in the lists than that cookie cutter version so I recommend using the above principles to get a good combination of the unit type that 'grab' you and effectiveness. I also have this comment on some of the heroes in the evil list:
YMMV