Welcome 
Firstly, a slight tweak to your terminology will help you get positive reactions to your posts; we've 'powers' here, not 'spells.' And outside of people calculating melee attack chains for absurdly hard targets, there's really no such thing as rotations in CoX. Since team composition and battle situations change constantly, I find myself adjusting which powers I use when on the fly.
Plant/kin are combos i've played separately but not together, and i hear together they're great.
Crucial powers for Plant/ are Strangler (single-target hold), Seeds of Confusion (fast-recharge AOE confuse), and Carrion Creepers (an invisible AOE slow/dmg/knockdown/immob pet). Probably Roots (AOE immob) as well, as it causes a big chunk of dot and sets up easy containment. All of these powers are the backbone of your control.
Vines and Flytrap you should also take; Vines is a slow-recharge AOE hold, if things are going south and Seeds is still recharging, Vines gives you another option. Flytrap is extra damage that you dont have to think about, and gives mobs something else to punch.
Entangle, Spirit Tree, and Spore Burst are skippable, IMO, but you may get personal use out of them. Entangle is a good single-target attack. Spirit Tree is useful to add AOE regen to a team fighting hard targets (AVs, etc.), but nobody's going to care if you dont have it. Spore Burst is an AOE sleep, and since sleeps break on damage, is an unreliable team control.
For /Kin, nearly everything is useful in one way or another.
Transfusion (foe-targeted AOE heal, debuffs regen),
Siphon Speed (foe-targeted self +spd/+rech buff, foe -spd/-rch debuff)
Speed Boost (short-lived +speed/+recharge/+recovery team buff),
Transferance (foe-targeted aoe +end/foe -end),
and Fulcrum Shift (AOE +dmg/foe -dmg),
are pretty much what makes Kinetics great. Siphon Power is great early on, and still finds use in debuffing hard targets. Increase Density offers some team dmg resist and status protection, Inertial Reduction is a superjump buff, and Repel is the redheaded stepchild of the set, that is fun, chaotic, and sometimes causes as many problems as it solves, heh.
I would make sure i had 5-6 slots in Seeds early, so that it had good acc and was recharging quickly. It can be up every spawn, and is excellent control. Stack holds on bosses, get good at clicking a target to use heals or debuffs on.
Generally, it is probably wise to make sure you have 2 powers from the fitness pool so that at lvl 20 you can pick stamina. Once you have transferance, you might be able to go without stamina, but life is usually easier with it.
above all, have fun
50s:
Grimmloch, Tactically Delicious, Ugly Frankie, Operative Tracker, CryoFurnace, Professional Help, Silver Sphinx, Aries Knight, Tachyon Aegis, Jade Sphinx
Currently building:
Any one of half a dozen alts!
Thx for the welcome 
I used the word spells because I usually play the traditional mmo's, not going to make that mistake again. 
Thank you for your very informative and helpfull reply, this will help me out a lot with what powers to take or to skip. 
Hi all,
I'm a new player to coh so I still need to figure most things out atm.
But I decided to roll a Plant/kin controller (lvl 8 currently) but I don't really know what spells are any good for plant and kin, atm I'm just selecting a random spell when I train and see how it goes.
I also tried to look for some good build or guides but most build are about farming and the guides were very old.
So I hope someone can push me in the right direction with a build for leveling and team play.
And any help with a rotation would be great also
I will ofcourse learn more about the class and playstyle on my way to 50 but atm I could really use some help.
thx