Ok so a quick introduction. I won't be getting in depth with many things, you can change the guide to your liking, but I find this guide to be an epic late-game guide AND very good early. As you can see I didn't put the wards in, I'll get to that in just a little bit.
So for this guide, as a support, you'll want to have a good slower/stunner to be with you. I find botting with lux or ashe for example to be a good combo with blitzcrank, although I must tell you I used this guide online and any champion the other guy uses to go bot usually does nicely, it all depends on those Q's hitting the enemies, if you're a sharpshooter then you won bot lane.

I hope you find it helpful if you're new to blitzcrank :).

PS- With this guide you can play VERY aggressively at late game.

So no runes used in this guide for a simple reason - I don't eaither. I'm level 22 and still haven't bought any, so if you do are planning to use runes I suggest runes in the line of cooldown reduction, mana regen, health regen and movement speed. But this is absolutely up to you

The masteries. Yes, a little bit odd for support, but that's because you'll also be tanking. I guess you could use some points in the support "lane" of the masteries up to the ward one or the movement speed

I use those masteries to play with RANDOM players. If you're playing with a premade team and want to combine some better masteries to go better with the champion you'll be supporting then it's best.

Edit: The point on "Summoner's insite" will be explained down in the summoner spells"

So this is where it starts getting tricky.. The skill sequence depends mostly on the game. For example, if you're playing more defensively then I suggest using some extra points on the "W" at early-game for running faster.

To give a quick brief of why that, "random-like" sequence, well, as you see I get three points quickly on E. That's because early-game you won't have any cooldown reduction items for a while, so you'll want to reduce it by getting some points on the E. When you start getting the Ion boots and so on then you won't need any more on the E, usually three points are good because you'll mostly only use it when you pull someone.

After that it's just up to you, role between the Q and W depending on what's doing better - if you see the other team has fast runners/good slow downers/aggressive players then get a point on that W.
If they're playing defensively then you just rush in the middle of them before the burst of a team fight and deal a decent ammount of damage AND pull someone with that Q. So point early on that one if that's what's happening.

-Flash/Ghost, at your liking, for escape or pulling with Q purposes
(note that a well pointed flash with a Q is most of the times fatal to the enemy that's hiding behind the turret if your carry helps)

-Exhaust/Clearvoyance/Promote

\\Exhaust//-If you want some good pulls because your bot partner won't be slowing them down too much, or because you're new to blitz, then I suggest exhaust, to which, then you should get a point on "Summoner's Wrath" on the masteries"

\\Clearvoyance\\- I suggest this when you're playing with maybe 2-3 friends, if you're a good player and want to avoid those damn junglers, then use this instead (because random teams don't usually have junglers).
NOTE: In the beginning of the game, if using this, buy the first items ASAP and run towards your lane bushes, and see if your carry keeps up with you. Begin-game pushes are DEADLY and often determine right away the lane WINNER.

\\Promote\\- I use promote for late-game lane pushes. If you ever control one maybe two lanes and the other one is too pushed towards your nexus and you want to pull it off, then kill 2-3 armies of minions and use promote and you're done. (NOTE: With your ulti having a cooldown of 25s or so you should use it to clear minions quicker when alone pulling lanes at late game - BEWARE GANG BANGS, quick pulls and promote and GTFO to your team to the team fight!)

Since this is meant for a more informal gaming, more solo, less premade, then usually the clearvoyance should be enough.
If you'd prefer wards to pots, then you can also cram some in there.

Well, since you're support and you're blitz, you'll want a decent cooldown reduction for quick fatal pulls, so that's what I go for here, lots of cooldown reduction.

The manamune is for damage and mana. As you know blitz has it's passive which is mana barrier, which depending of the ammount of mana you have, he'll create a shield. So with manamune (and not only) you can have a decent ammount of mana and doing great damage spamming those skills. You barely waste any, in fact, I GUARANTEE you at late game you can spam the W to run around like nuts and barely waste any mana, seriously. And if you get into a team fight in between you'll still have a lot of mana to make a shield with.

The sunfire cape, well, save it for last, but it's great health and damage for team fights.

After that it's up to you - I suggest a Thornmail if you're going tank-ish, because at this point you'll be good with mana, and two tanks is always better than one, but up to you.

EDIT: The thornmail also helps you LOTS against ad carries, so you can almost 1-1 them and, if you're good enough, kill them. (at late game obviously)

EDIT: If you can, use some of those 100-200gp left you get off buying some items to buy mana pots and health pots. More mana at early game, more health as it progresses

EDIT: You can buy boots earlier if necessary

Pros:
-Great cooldown reduction
-Great supporting
-Good damage
-Great team fight endurance

Cons:
-VERY, VERY item reluctant. If the game doesn't go your way and you can't really do these items, then you'll probably LOSE. Items here are CRUCIAL for blitz.
-VERY bad for running away at the very beginning - until you get those boots you'll be as if "naked"

-ALWAYS use E after pulling someone with Q with Blitz. You'll see that with this guide you'll be able to do that A LOT with the cooldown reduction.

-You can use that arm of yours to pull enemies on the other side of structures, so when you're pulling the last turret before inhibitor, if you have clearvoyance you can send one in into the wall in the other side to check for enemies, and quickly pull them, with your team there it's insta-ko. 100%

-Try staying in front of your team when in team fights. If you get focused you can flash back after taking some damage, and maybe pulling someone, thus enabling your team a free kill. That mana barrier is crucial.
-Side note on this tip, always aim for the most feeded, focus on him ASAP and win the team fights easily

____The Ulti Passive____

-You can deal enormous ammount of damage with your ulti's passive, so only activate it if you have an enemie that's using an attack that lasts long (eg:warwick ulti, morgana ulti), or you want to finish enemies off, OR if they're running away and you can't stay near them anymore.

I hope you enjoyed the guide, give me some feedback after using, good or bad, all is good. If you have a good idea for a change then please, go ahead and post it

NOTE: Thia guide ended up longer than it was initially supposed to be, so sorry for that.

NOTE": Personally, when I use guides I don't read the "walkthroughs", I just see the builds and check the skill sequences, but since this guide is a tad more complicated, if something goes wrong then I suggest actually reading.

Hope you enjoyed it!

Good pulling!

If you're lazy (like me) then crucial topics here:
-cooldown reduction
-great late game
-carry reluctant at first but independent 1v1 later on
-great tanking
-great suppporting
-item reluctant
-very moldable guide