Hello,
I am need of some help on building skarner so far i build like this(Jungle):
Regrowth Pendent +1 hp pot>Pilo Stone>Boots (Zerkers or Merc)>Sheen>Warmogs>Triforce>Atmas>HextechGunBlade >Sell Pilo get BV.

Now the thing is i wanna build a Manamune on him cause he has mana problems with out blue, and he spams his Q a lot so it would build up fast, just i dont know when to get it or if its good.

So any suggestions?

Skarner is one of my primary junglers. I would not recommend building manamune. It takes too much money and leaves you too squishy for too long. Start with either regrowth or boots, then get philo. If fed, go for sheen then heart of gold, other order if not. For tanking, randuin's omen and frozen heart are especially good, and shurelia's reverie is also excellent. Triforce is your main damage source. Hextech and atma's aren't needed most of the time.

Frozen heart is pretty much core on him. That+Philo/Shurelia's should take care of your mana problems. Wits end and triforce is about the only damage item you need, and I typically replace the wits end later on. I go double gp5, and boots and then if I'm ahead and my team has someone else for primary initiation I go sheen, other wise I get a glacial shroud and some mr+finish my shurelia's. At this point I pick up my sheen if I haven't already, and finish that into a triforce. Mercs, tf, fh, Shurelia's, fon, wits end is my typical end game build.

Just had to put my two cents in here...

I usually find that my damage and tankiness only increase moderately when I upgrade the Sheen in to Trinity Force. I'm not saying that you shouldn't build Trinity Force but I am saying that you should have your entire core build before you consider upgrading it.

Skarner doesn't really have mana problems. If you get a philo stone, that pretty much is all the mana regen you need for the whole game. I play jungle skarner a lot, and I am often giving away my second blue buff because it just isn't necessary. A few good tips are, if the jungle camp is always dead auto attack are pretty ok to use. Don't do a w q combo for 3 bruised wraiths. If you have three points in expanded mind, that helps a lot too. Also, don't put a point in e pretty much ever. Its a mana dump and isn't worth it for fairly ****ty dps. Go q and w all day, and b happy. Skarner is a pretty spam happy champion. Just know when the spam is worth it and when it isn't.

The rest of your build looks fine. I prefer ninja tabia on skarner because they boots are cheaper, and it makes ganks a lot more likely to go in my favor. Merc treds are necessary because when you build warmogs, high health is a great soft counter to magic burst damage. I also like to build sheild of ageis before warmogs, because it helps your team out in the team fight, and it puts your MR and armor at about the magic 100 mark, which is good defense and wonderfully cost effective.

unholy grail was made for skarner :P

that alone solves any mana problem at all, the regen rate on it will forever allow you to spam crystal slash non stop, it'll also provide a good amount of magic resistance and the cooldown reduction in conjunction with either frozen heart/nashoor's tooth (which ever you prefer) will give you max cooldown reduction without any runes or masteries. the core items I'd start off with is boots sheen and chalice, in any order you find most useful, I dont even bother upgrading sheen since 100% every 2 seconds alone is good enough, getting all the other essential stats is more important. upgrading chalice only after your attack speed is high enough that your able to cast crystal slash every second.

avoid buying mana items if you get chalice though, you want the high regeneration at all times and the higher your mana is, you'll have to bring your mana down lower in order to get that higher regeneration.

but yea, unholy grail is a great item for skarner. worth taking a look into it