i am going to necro this thread, it isn't that dead, and i think we need more talk on the elven recruitment, and associating play styles (as those two are quite related).
knowbuddyuno presented a pretty good way of dealing with rank and such, personally i solo mountain goblins until the war starts, then i head to elven lands and grab quests. i like the killing scouts one at this stage, but be sure that you always fight with allies, as you will be too weak on your own to solo them (well if you are not horse archering them), it also means that you can hold your troops behind the allies troops and help increase their lifespan. before you reach a decent rank, you should have enough troops to turn the tables on the largest groups of enemies that are attacking allied patrols and such. don't be too greedy with army size, as bigger armies don't move as fast, and all you need to be able to do is help allies out. focus your influence on more permanent things like gaining heroes, and weapons. by the time you crush the opposition in elven territory you should have nearly maxed out rank if not maxed out, and more importantly your army, having survived through many battles will be of decent rank, which means a small elite group which can handle those sneaking quests better than the humans or orcs.
when you venture into human lands, the battles will be easier than when you were a human, since your group will be based on support, and at elven levels as well. start with rohan, and once their enemies are crushed, move onto gondor. there you might face the four hosts (if they are turned on), which will be your toughest opposition, well other than the attrition of being so far away from elven reinforcents for your losses. since gondorian forces are pretty good, you might pick up some gondorian archers and such, brute force is what is most needed at this point, so the trade out won't hurt you much at all.
what makes the elven war easier is the lack of pows that your allies carry around, in human lands if you are a big help then your allies' parties slowly diminish, while their prisoners grow. eventually they take a loss and that loss is worse than when the elves take a loss, do to how much men the orcs get from rescuing pows. a lucky enemy might get one group to bolster its forces, and then move unopposed against other weakened allied forces, resulting in a chain reaction which causes a patrol to become as big of a threat as a war party. in elven lands the reverse happens, each victory bring the victorious party closer to defeat, so that a war party with a string of victories might not be much more challenge than a scout. once you realize this elves are fairly easy to play, as they enjoy the advantage of being able to cycle their forces without aiding their enemy. the orcs have the advantage of being able to cycle their forces without bringing them as close to defeat. keeping these in mind you can make the "weaker" easier to play, just by changing your strategic objectives.