My second attempt for a Shen build. First one was archieved, due to changes of gameplay.
After trying some new combos, I've successfully come up with a balanced tank build for Shen, the Eye of Twilight.
The build is far from being perfect, only reason I posted it is because it really worked for me and maybe it will work for somebody else.
I won't post any game screenshots (cause I didn't take any) but trust me, I got cursed and thanked for playing (quote) "AN EXCELLENT SUPPORT". I'm quite proud of myself as I got one step closer to being a better League of Legends player. I normally die while protecting others, but these past times I managed to stay alive and protect my teammates in the same time.
Dunno about you, but I think that's what a tank supposed to do, if possible of course.

CORE ITEMS!:
Mercury's Treads , Thornmail , Sunfire Cape ,Force of Nature ,Guardian Angel

Situational Items!: (if you're missing something from the build or have a free slot to fill)
Randuin's Omen ,Frozen Mallet ,Quicksilver Sash ,Spirit Visage

Candy-man! (if you're doing well but teammates aren't)
Aegis of the Legion ,Soul Shroud ,Shurelya's Reverie

Identity Crysis!: (you've got fed but you still lust for kills)
Rylai's Crystal Scepter ,Zhonya's Hourglass ,Abyssal Scepter

I used to run with Ignite and Ghost (or Flash ), but I decided it's best to help my team as much as I can, so I changed them to Teleport and Fortify .
Fortify got me more kills than Ignite used to, and it's amazing how 2 tps (Teleport and Stand United ) can drive ppl crazy.

Cleanse is always welcome against heavy CC's.
Another useful Summoner Spell would be Exhaust

Masteries are set around Defensive build (dooh).
I found Ardor useless, as I could distribute those 3 points in something more useful.
Picked the usual tanky build, except Strength of Spirit --> useless on Shen cause of his energy (instead of mana) system.
Harden Skin+Defensive Mastery are good early game when dashing towards enemies ganking a teammate (sometimes through creeps).
Veteran's Scars goes well with the Ruby Crystal and Hp Quints in early (even mid) game.
Reinforce is nice as you can defend your turret better against minions when Fortify is on cooldown.
Tenacity is a must (at least imo) for a tank champion such as Shen (quite useful for anybody but, luckily, they're not all tanks).
Picked up Spatial Accuracy instead of Haste, Good Hands instead Perseverence (3 points only for total health regen increase... no ty; it would've been viable if I had mana..)
Awareness is not a must, but the xp gain is quite nice so that's about all regarding Masteries.

THOSE ARE NOT PERFECT RUNES. I just made the terrible mistake of buying them without doing any math. I ended up with them, and all I can do is use them til I get enough IP to change some/all.
Picked what I thought (at that time) would be best for a tanky Shen : dodge, armor, magic resist and hp.. Sue me for being hasty, hehe.

I'm not sure if the skill sequence is accurate, but you can always change it when you face your opponents --> Vorpal Blade maxed first and Feint later for melee champions, Feint first for casters, and so on. I repeat, not sure if I distributed the points right, according to level-up possibilities!!

Items:

Check CORE ITEMS before reading this!
Last two items are SITUATIONAL -->> this means they can be replaced with anything you might require.

Normal Start.
-Start off with Ruby Crystal and turn it asap in Heart of Gold
-Buy Boots of Speed and get Chain Vest .
-Turn Boots of Speed into Mercury's Treads after completing Thornmail
-Grab Giant's Beltk if you don't lane against AP champions; else, get Negatron Cloak
--If you're getting Giant's Belt , sell Heart of Gold
-Complete Sunfire Cape
--If you've went for Negatron Cloak , sell Heart of Gold and get Force of Nature .
By now you should have your CORE ITEMS up and running.
Depending on the your needs, get whatever suits you best from SITUATIONAL ITEMS

Depending on the teams you face (on your lane) you can easily get Doran's Shield instead of Ruby Crystal , if you think you can't manage to dodge their attacks.
As you can see, SHEN HAS NO MANA, therefore NO Doran's Ring ,NO Chalice of Harmony ,NO FROZEN HEART , NO Banshee's Veil

AD Composition?
Get Randuin's Omen ,Frozen Mallet
Mixed Composition?
Get Guardian Angel
AP Composition?
Quicksilver Sash ,Aegis of the Legion ,Spirit Visage

I never knew exactly what to type here, mostly because I lack sufficient informations to prevent me from comparing Shen with other tanks.
However, I will give it a try:

Pros:
- good survavibility early and late game
- decent damage for a tank (especially returned magic damage --Thornmail )--
- high mobility due to teleports (spell and skill) and the movement speed bonus of the Force of Nature

Cons:
- not enough magic resist early game
- not many bonuses given to the team through item build.

Throughout my games I rarely got any buff for myself (except Baron, ofc) and I tried as much as I could to 'ping' my teammates when the buff holder (creep) was close to dying and allowed him to finish the job, thus gain the buff (whether blue or red, depending on their needs).
I would advise you to do the same.
Call me stupid or noob, but I'd rather help than get stuff for myself.

As you can see, I don't have a ward system, mostly because I'm still figuring it out. It's not complicated, but I'm not yet fully informed on placement and time to place, so I decided to skip it instead of saying smth wrong.

Comment is required to vote. No trolling, positive criticism is welcomed. Would be nice to try the build before downvoting.
Ty.