Agreed. There isn't a lot of variety in the forces of Mirkwood but don't let that discourage you. They are effective and can be very fun.
Always max out on your bows. You will find WE Spears are a great option since they give you a defensive option (Shielding) as well as support and direct offense.
Throwing Daggers are great for boosting your ranged combat abilities and are recommended highly by many of us. You'll find the best balance of number as you play and get your own style, but I usually give TDs to any of my WEs that aren't using a Bow or Spear (and even the Spearmen sometimes get some). You can usually treat the WE models with swords as just being armed with 1H weapon and be fine. If your enemy has a lot of high armor though you probably want some Elf Blades mixed into your force to help chop them up.
If you are playing at a point level where you have either a WE captain or Thranduil (he's GREAT for his price...you'll learn to love his special rule and he's a good combat leader with a 2+ shoot), then take Legolas as an "ally" from the Fellowship list. This lets you give him armor and helps his staying power. If you can't then give him an Elf Cloak if possible.
For games of 300 points or less you probably dont' want to put points to a Sentinel. From 300 - 500 you can generally get one without hurting your numbers. At 500 and above always have at least one. Once you get to 750 points two Sentinels are fine.
WEs give you the chance to have lots of models while still getting the quality of Elves and this can be very powerful. Your D3 will be ripped to shreds by most Evil armies if you give them a chance...so don't.
Shoot and scoot. Use Spears to control one-on-one fights (shielding gives you great odds of winning the Fight) and try to take your enemy models on 2-on-1 or better.