what genie best for sin?!?!

tangling mires better than extreme poison for a sin in most circumstances. Especially if you have second wind on the same genie. Both strength based skills. Only get extreme poison if you make a dex genie.
Personally i have several different genies. Pve, ground pvp, air pvp etc.

You will probably want holy path on all your genies, good skill, nice speed boost, useful in pvp and pve.

Second wind or tree of protection are nice for the added heals and can be used in pve or pvp. Second winds great at low lvls as it's an instant heal unlike tree, but at higher lvls when you get decent hp tree will heal you for way more and the heal off second wind will be fairly negligible by comparison.

Tangle mire and extreme poison are good for increasing your damage. Tangle mire is an aoe, so you can hit lots of mobs with it, it lowers the enemy's pdef and is strength based. Extreme poison amps the damage the target takes from all kinds of damage, but can only be used on one target and is dex based.

Bramble rage is a great pvp skill, nice to be able to do magic damage against ha's and other la's. It's also a nice addition to your aoe's for pvp/tw and has some pve use. It's dex based, you also need a fair amount of vit in your genie to have the energy to use it. Only usable on the ground.

Occult ice is really good for pvp, stuns the target. It's strength based, without a very high str genie it has a really high chance to miss. So if you put this skill on a genie make sure it has a lot of strength.

Absolute domain is a must for pvp and very useful in pve. Stops all damage for a few seconds, then makes you immune to stun for a couple secs after. Great pvp skill to use when someone stuns you or when you see a hard hitter channelling an ulti and you can't stun them/sleep them/seal them or cancel their channelling etc.

Expel is good too, kinda like ad but it just stops physical dmg. You seal yourself when it's on so you can't do anything, but it lasts for ages giving you time to run away a bit. Good move when you get stund by a bm or sin. Has a way shorter cooldown than ad. it's actually only 1 second. So as long as your genie has the energy you can sue it.

Frenzy can be nice in pve to max your damage, but be careful with it, don't use it on something you can't tank easily. As it increases your damage but makes you get hit harder.

Errrrm, there are other useful skills for specific situations but those are the ones i find myself using most frequently.

On me pve genie I have tangle mire, holy path, tree of protection, AD and enflame so i can lure stuff. It's a mostly strength genie with enough vit to use all the moves and enough magic to get decent regen.

Ground pvp genie I have bramble rage, holy path, AD, Expell, tree of protection. It's dex with high magic and enough vit to use all skills. I use this one in tw to aoe people with bramble rage.

My other pvp which I use for aerial pvp is a strength based genie with occult ice, ad, expell, tree of prot and second wind. Don't use this one very much, I don't really like to rely on occult ice as it misses a lot even on high str genies.