Welcome to Librarium Online!
as said in the title I am starting an Eldar army which is my first Warhammer army by the way and I have a few questions and I hope you are going to be able to help me out.
For now I have the Eldar Battleforce and I am starting building ...
1 - What do I put on my Wave Serpent? What kind of heavy gun is the best on those vehicules? Are there any upgrades I should put and some that I should not?
2 - For the Dire Avengers do you usually purchase Bladestorm and Defend? For the equipment I will check "Trick out your Dire Avengers" post it seems pretty complet.
3 - What is the best weapon for the Heavy Weapon platform in the Guardians squad. I think I could make swappable, but I still want to know. Starcannon seems for Space Marine, Scatter Laser for swarms and EML for all-round purpose. Shuriken canon not really interesting. For now, I would chose EML because of its versatality.
That is it for the questions.
My main opponents are going to be :
1 Orks (with lots of Boyz and Nobz for now)
2 Space Marines (one with lots of anti-tank guns, not many vehicules and terminators and the others Drop Pod oriented)
1 Tyranids (with Gaunts, Carnifexs, some Tyranids Warriors and Lictors)
Thank you for your answers
For the wave serpent's weapons, what I use generally depends on the unit it is carrying. Assuming that you will be putting your dire avengers in it, a scatter laser could be helpful to rack up even more kills against hordes, as that is the favourite target of avengers. Alternatively, in small forces such as this, it can be helpful to use every heavy weapon possible to counter heavier units, as avengers and guardians can handle light infantry on their own pretty well (missile lauchers are great for getting auto-kills on those pesky 2 wounds nobz you'll be facing). Spirit stones are pretty vital for transports, as it will help to ensure your unit gets to where it needs to be. vectored engines will increase the survivability of the tank considerably and are quite helpful if you have the points.
Both exarch powers are awesome. Defend is perhaps less necessary if the unit is mechanized (you can get them out of sticky situations), but still a good precaution.
For the guardian platform, I suggest not definitively choosing a weapon just yet. It's easy to place the weapons on the platform without gluing them down, so try the different weapons in games until you get a feel for which ones work in which situations (this could also be a good idea for the wave serpent weapons)
There's three main builds for these guys. There's the Shuriken death route, which uses 2x catapults and bladestorm on the exarch while riding in a wave serpent. Then there's the footslog variant usually takind defend and power-weapon + shimmershield combo. The last build is the mixed build taking whatever choice felt neccesary for weapon and taking both powers. Whether a transport is utilized usually depends on the weapon choice (e.g. footslog ONLY if using the shimmershield + power weapon.) Actually, there's four builds, but the fourth isn't really a build, it's more of a strategy, since it relies on massive amounts of dire avengers with no upgrades whatsoever footslogging across the field(usually only seen in pure footslog armies.)
Depending on what units are being transported and personal choice/army list needs, Wave Serpents are fitted with various weapon options. The most common are the following:
Scatter Laser - Used to cheaply outfit a wave serpent while keeping a decent range and firepower capability. Usually used in highly mechanized armies where there is no need for additional anti-tank weapons and used to keep costs down across 4+ Wave Serpents.
Eldar Missile Launcher - Usually used in hybrid armies where there's a need for versatile weapons due to different parts of the army moving at different speeds causing a need for groups of units to fulfill different roles in a pinch. Also used in conjunction with the underslung shuriken cannon due to it being the only weapon you can mover over 6" with and still fire both (using the Str4 missile and the S6 cannon.)
Bright Lance - Usually used by Eldar players who do not run wraithlords, as this is one of only two other reliable sources for heavy anti-tank weapons, the other being two Fire Prisms firing together. Often used in mechanized armies utilizing Fire Prisms, as the Prisms can take up the role of template death that the EML would otherwise fill (although the EML isn't as effective since it's a small blast, but it is a blast nonetheless.)
Shuriken Cannon - Not used unless you ABSOLUTELY cannot afford a Scatter Laser, the Shuriken Cannon is just not worth the points. (on top that is.)
Starcannon - Sort of a niche weapon, it will almost always kill things without an invuln save due to its Str6 and AP2 shots. It's fallen out of use since the 4th edition nerf bringing it down to 2 shots, and it's almost non-existant in 5th due to cover negating its AP2 making the cost of the weapon hard to justify.
Spirit Stones - Pretty much a must-have for the Wave Serpent as not being able to move cripples the Eldar's ability to strike in unison
The other upgrades I don't have any experience with, but a lot of people take Star Engines for the ability to get from one board edge to the other in 2 turns.
Eldar Guardian Heavy Weapons
The general agreement here is that you take the Scatter Laser as the high rate of fire ensures a decent amount of hits with the guardian's poor BS. A few people have taken EML's and used the Str4 template to get around the bad chance to hit normally, but the high points cost doesn't make it worth it. Bright Lances have been used, but very rarely, and usually only in a tournament where lots of AV 14 will be present, as they're very spendy and only one shot. If you can get anti-tank somewhere else, I suggest you do, a 50/50 chance to hit isn't a chance I'd take in an all-comers list.
Scratchbuilding Fire Prism Crystals
2K Mech Eldar in 2010: 25Win/4Lose/8Draw