Great job for a first guide, I don't even know how to make one right now (since I actually just made an account to comment on your guide). However, after reading your guide, I feel that you have heavily misunderstood the reason Jungle Ezreal is picked.

Jungle Ezreal has no form of CC, squishy (since he is traditionally a Marksman), loses a lot of health in the early game when clearing jungle camps (which only got worse due to the fact that Season 4 changes means you must clear 3 jungle camps to hit Level 3), heavily snowball reliant, has difficulty building up items and several other poor qualities of Jungle Ezreal continues. He does NOT fit into many team compositions as you mentioned.

The pick of Jungle Ezreal is for the reason of SNOWBALLING HARD early game, SIEGING TOWERS and SPLIT PUSHING. This means that you will not be ganking very much. Instead, a Jungle Ezreal is best for pushing down towers very quickly, ending the early game (which a Jungle Ezreal will have many problems with) fast, then continue to apply pressure on a lane while the rest of your team pushes another lane. This means that Jungle Ezreal is very dependent on the team and needs a good start to be effective in a game. Another reason why Jungle Ezreal is picked over other junglers to fulfil such an objective is because Jungle Ezreal brings something to the table that many junglers do not have : Range. This allows Ezreal to safely push a lane without having to get very close to a tower to deal damage, putting him in a compromising position. Coupled with the fact that he gains increasingly more attack speed with his passive, he can down a tower very quickly. Also, since he is extremely mobile, he can apply pressure across the map, when a lane gets too heavily guarded and he goes to push a different lane. Since you will need Dragon control, these lanes would be the mid and bot lanes that you will be pushing.

Now, to first fit a Jungle Ezreal into a team, you have to fill up gaps. The team that Jungle Ezreal is in must have several qualities to survive laning :
-The top laner must be able to handle almost any 1v1 matchup and be able to escape from ganks. In short, he must be able to at least break even in a lane and escape from almost any gank. A good pick would be Renekton. This is because you will be pushing the mid and bot tower the whole game and thus your top will be vulnerable to enemy ganks. If the enemy top laner gets fed, the snowball strategy won't get you anywhere since you have to be the one in control of the game.
-The mid laner needs to have good CC and be able to assist you in tower siege. Picks such as an AP Janna mid would be good since her Eye of the Storm gives you additional AD to take down towers even faster. The mid turret would be your first aim anyway, since it is a solo lane and the shortest lane in the game.
-The bot lane must have strong CC to make up for your lack of CC as a Jungle Ezreal. The matter of having CC is rather self explanatory so I think you understand this point already.
-Obviously, your team must be able to work together and go along with the plan of having Jungle Ezreal. If your team is going to flame you for taking their CS when you try to push a lane to siege towers, you're going to lose the game.

Now, this is my personal opinion just like your opinion of the role of Jungle Ezreal is to fulfil the goals that you have stated in the guide. Perhaps it may work like how you use it, but from personal experience I have to say that it is not very effective. Other junglers are much better unless you are able to meet the many conditions that I have stated, if not more. I have had games with Jungle Ezreal in Ranked which were successful, but most games were rather rough in the early game as I was pretty susceptible to counterjungling and Ezreal could not duel most of the traditional junglers I faced. Comebacks are definitely possible, and I have had one of the most dramatic wins after a comeback myself, but it is very difficult, especially if your opponents push their advantages for the win.

That aside, I feel that you could make a little change to your rune page. Since you are jungling, attack speed is more valuable than AD when clearing jungle camps early on. Thus, attack speed marks can be more beneficial than AD marks. You can balance the two if you like. With Season 4 changes being introduced, it will become even more important to have this quicker jungle clear time since you have to clear another jungle camp after your red and blue to hit Level 3. The other runes are perfectly fine though.

As for your masteries, well the explanations are obviously incomplete. For your offence masteries though, I feel that investing points into Blade and Spell Weaving are much better on Ezreal, since you will be weaving in Autoattacks and your Mystic Shots to fully maximize your damage output. Obviously this will mean changing the mastery page a lot more from yours though.

A little note in the skill sequence would be that leveling Essence Flux at Level 8 is kind of a waste. You're better off with another point in Arcane Shift as Essence Flux has low damage and no longer provides the extremely useful effect of decreasing the enemy's attack speed ever since the nerf.

For the item choices, I have to highly disagree with some pickups that you mentioned.
-You should not pick up Iceborn Gauntlet AND Trinity Force. Even if you are extremely far ahead. You should only pick one and if I had to choose, I would favour Trinity Force. Sure, Iceborn Gauntlet gives a nice slow, but you already bought Spirit of the Elder Lizard for a slow. No point getting another slow item, especially much later in the game when CC should be coming from your other teammates (who should already have a decent amount of CC to cover up for your lack of CC). The point of buying SOTEL is to have the slow early for ganks but if you further your item build into an Iceborn Gauntlet, which provides no AD at all, it just hurts your damage output. Trinity Force is much better, especially since it synergizes extremely well with your kit.
-Infinity Edge may not be a very good choice for Ezreal since his Mystic Shot does not critically strike. You do still AutoAttack but other items may be better. Just my two cents worth.
-You should pick Bloodthirster over Blade of the Ruined King. Looking from your explanation it seems like you want to be as slippery as possible. If that's the case you might as well pull out a Blue Ezreal which takes a lot of time to ramp up power. And that doesn't work out at all if you ask me, because your Tear of the Goddess/Manamune takes so long to stack anyway. The tank shredding potential is nice, but since you aren't as Autoattack reliant like other Marksmen, it doesn't work just as well. I feel like it's more of an item a traditional Marksman Ezreal would build if his team composition is kind of focused on an all in comp while you sit at the back continuously throwing Mystic Shots and weaving in Autoattacks as well, since he would have nobody peeling for him and the active of Blade of the Ruined King helps. In any case though, I think the item is better for a traditional Marksman Ezreal. Furthermore, the only core item that gives you decent flat AD in your item build is an Infinity Edge, so you wouldn't have very good flat AD with that build. Bloodthirster stacks push the AD you get from the item to 100 when fully stacked anyway. If you are looking for DPS on a traditional Marksman as a Jungler, you should go with Twitch. He's the only other Marksman that can fulfil a Jungler role if you ask me.
-For the possible pick of Maw of Malmortius, it's more of an item you get if you are far ahead. If you really want to get some defence against magical damage, you're better off buying a Guardian's Angel for MR plus the passive, or get a Banshee's Veil when Guardian's Angel passive is down.

Other than those items I think your other item choices are okay. For the Mercury Threads though, you should state that it is if the other team has a lot of CC, not just centered around you. Besides, even traditional Marksmen sometimes get those boots over Berserker's Greaves if they really need it.

For the Jungle Clear routes, I think taking Red buff right after Blue buff is still better than taking wolves after Blue buff. As a Jungle Ezreal, most junglers would already try to steal your red unless they are pretty weak early game themselves like Amumu. In fact, I think that if your team will help you, you should invade one of the enemy buffs. Jungle Ezreal is already a big shoutout for the enemy team to invade most of the time. Vertical Jungling (stealing one enemy buff and then taking one of your buffs) would be safer in my opinion. It's really just the same idea you pull when the enemy has a Blitzcrank who will probably just hook out your buff. And in that situation there is no way you can defend that buff.

I won't comment about the part about ganking because I already said that my opinion of Jungle Ezreal is to push lanes. The last part on Gameplay seems fine.

Anyway, if you actually bothered to read this gigantic chunk of text, that's all I have to say. If whatever I said seems in any way insulting to what you have written, no offence, really. I main Ezreal myself and this is just my two cents worth. Good guide overall, and hope to see the new updates too. I'm Gold 2 and play the same server too. Maybe we could talk or duo together sometime.

Seal, can you tell me if Jungle Ez is still viable in Season 4? because Spirit of the Elder Lizard seems weaker than ever and the recent nerfs to it removed the free procs we used to get from our W, E and R. Would the most viable option right now be simply pick up a Wriggle's Lantern for a more farm-oriented jungle? Or even a Spirit Stone for the regens but never upgrade it? rushing a madred's and not upgrading it is also quite viable. I would like to know your opinion on these. Also, if i'm not mistaken, Spirit of the Elder Lizard has no CC attached to it, it's proc only burns the target with true-damage; different from blessing of the lizard elder (red buff) that also slows.

Well you haven't add trinkets yet lol.....