Hey there :D Looks like a thought through champion concept ^^ Lemme give you some feedback on that :)
A word of caution: In the first part of my review I will mention a lot of faults or shortcomings in the kit. Do not see this as me hating your champion!! I can see that you are new to the creation of concepts and I am simply here to help :) I want you to know that I really see potential in the kit and that you worked really hard to make it work!! I will list a few tips at the end for you.
General:
Since you did not make any lore yet, I'm having a hard time trying to figure out exactly what thematic Ruh Alev is supposed to fit in. For now I'm getting a real Lee-sin meets Ryze vibe (with the kicking and the mana scaling). In league, many kits and such match the thematic or the lore in some way. With Ruh Alev however, I get the impression from the names of his abilities and such that you want him to be a sorcerer of some kind...while at the same time he has a kicking move and an auto attack enhancing ultimate. I also get the impression that he is Melee range (although you haven't mentioned the range anywhere). These things don't resonate thematically...sorcerers are usually people that unleash powerful magics upon their targets, not people that kick and punch their enemies. Maybe you could use a different word in stead of Sorcerer or maybe add a lore section to create a link between his abilities and his thematic :)
I also sense that you want him to build hybridly, seeing as some of his abilities scale with both AP/Mana and AD...In reality, it's usually never good to build half/half, even with hybrid champions...so make sure that your kit works even when building pure AD or AP!!
His stats:
I am curious whether you intentionally gave him an incredibly low base health stat (even at higher levels)...As comparison, look at Zyra's base stats. She is known for having the lowest base health in the whole game, and yet she still has 99 points of health more at level one then Ruh Alev has....at max level this difference even becomes as high as 557 points of health!! Thats a whole tank item worth of health!!! With a Melee attack range (still getting the impression that he's Melee range) and a Q like that, Ruh Alev will need a lot more health or some seriously powerful sustaining ability...
To tell you the truth, all of his stats are very low in comparison to other champions in the game...which makes him incredibly weak, even with items...
His passive:
This is the part of the kit that makes me believe you wanted to create a mage of some sort...And its a good idea :) The reduced AD scaling and the bonus AP on auto attacks is a nice idea (not unique per-say but still good). I'd fiddle with the percentages some more though....as of now I feel that he will be majorly underpowered early game (since, at level one, most champions do not have any AP). This will give him problems with farming and trading. This is not in itself a bad thing, but make sure he can overcome this weakness later in the game.
The second part of his passive needs some thematic reasoning behind it, but works aswel. It is a simple stacking mechanic. Maybe allow him to stack on minions aswel, since he's probably not going to get a lot of kills early.
His Q:
This ability has a lot of potential!! But not for a mage/sorcerer character...It reminds me a lot of Lee-sin, but still manages to be a nice and unique ability. Good job!!
The only concern I have is that the AP scaling begins only after 2 seconds of charging...thats a long time, and unless he can charge, save the charge and recast the ability when he needs it, I think that it will be pretty useless...People in league rarely stand still long enough for such an ability to land...even Vi can move during her charge (albeit slowly)...try and work around this!!
I'd keep this one and try to form his theme a bit around a magic using martial artist....but be careful not to come to close to Lee-sin's theme!!
His W:
So theres a number of unclear and weird parts about this ability...
First of all, he channels for 3 whole seconds to become invisible? That is a long time...maybe lower it.
Second, the time scaling "8/8/9/9/10" is very weird....you should probably use half seconds like "8/8.5/9/9.5/10".
Third, is the +1% mana a percentage? So with 500 mana, he gains 5% movement speed? or 5 flat movement speed?
Fourth, with a "80/100/125/150/175" mana cost, this might very well be the most expensive basic ability in the whole game...even most ultimates usually cost only 100 mana...And lets not talk about the gargantuan cooldown....
All in all an ability with nice potential. I like the fact that he can charge his Q while in stealth. The numbers are just a bit wacky.
His E:
This is basically a Bard Q, but with 3 champions in stead of 2 and with a slightly higher stun duration and incredibly low damage scaling...And Bard is a support mind you...For this champion to be a carry (cus I'm getting the vibe that he's not a support) he will need to do more damage with his abilities...
Other then that, the ability is fine.
His R:
Again I see that you are trying to make him a hybrid champion...this is fine, but this is very hard to balance...As of now, I'd probably build him AP, since most AP items have base mana stats aswel. Since this ability makes his aa deal 130% (which is absurdly high) and essentially 5% of his max mana in bonus magic damage, this ability alone would make him a borderline broken powerhouse...If his stats and the rest of his kit wasn't so weak (weak as in stat wise I mean)...
All in all a generic self buffing ability...I'd love to see something more interesting here...
Last notes:
As I said, I can see that you are new to creating champion concepts...That said, I can see very clearly that you worked hard on your concept and have a very clear picture of what you want. Additionally, you seem to be open to critique and feedback, which is always a plus on the boards :) Here are some tips to make this concept even beter, or to take into creating another concept.
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Take a look at the kits and stats of other champions that resemble his playstyle. Ruh Alev's stats are very underpowered, which can be very easily helped by looking at other champions stats (I usually copy the stats of my champions directly from a champion that I feel has a similar playstyle as my champion). You can also look for inspiration on damage scalings, cooldowns and mana costs in the kits of other champions.
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Try to craft a unique theme for your champion. Ruh Alev feels like Lee-sin combined with Ryze (with a sprinkle of Bard and Master Yi). You can do this by thinking: "What is my champions place in Runeterra and the game?" or "What makes my champion unique?" Try and bring that into words and see if your abilities fit that description.
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Let your kit, the lore and the thematic resonate with each other. Ivern is an ancient being and a friend to all living things...as such, his passive allows him to clear jungle camps without killing them...This makes sense and feels right thematically. Things like that are very important!! It would make no sense for him to start chopping down trees (for example) as an ability!!
I hope that I've given you some useful feedback on your champion!! I really hope that it will inspire you to make more and beter concepts in the future :) When you feel ready, try and enter the CCOS!! It is a monthly contest in which concept creators send in their work to be judged by anonymous judges and are ranked among their peers. My current entrant into the CCOS is Gaunt, Denizen of the Fog. I'd hope to see you there some time :)