The build still works well but nobody even read it so I stopped trying to make it better. Disregard most of the writing, I was pretty noob back then.

This is my first guide ever, I'm fairly new to the game (been playing about a month) and Amumu is one of my favourite characters (currently trying to learn Ezreal) and I play him when I want to farm IP because most games with this guy turn out to be wins. This guide isn't complete yet, but I would love to get tips on how to improve it! Anyways, here goes...

The order of the items were messed up when I first made it, changed that.

Need to add different builds at the top for different situations instead of just explaining it.
Need to add links and pictures instead of having a wall of text (if someone could tell me how I'd love it)
Need to add jungling guide
Need to add reasons for why I chose certain items over others

The reason I get bandage toss first is to compensate for if you get a ****** laning with you, you can save someone with the stun, maybe even get first blood (it happens) I try not to play aggressive because I feel pretty squishy until about level 4 but if your lane partner is doing great with the harass, feel free to try killing them since everyone is weak at low levels.

Flash has got me out of many sticky situations (pun intended) and is a lot more useful than ghost on amumu since his move speed isn't brilliant (hence the swiftness boots)
Ignite gets more useful than exhaust as the game goes on because of the increasing damage bonus, but if nobody on your team has it, get exhaust.

The other ones seem pretty **** to me, but summoner spells are best chosen for your own playstyle.

This is mostly common sense, and you change it depending on who you're up against, but the beginning items are almost the same every time (so is the ending depending on how long the game went)

I always start of with rergowth pendant and a mana pot, I turn that into a philo stone before doing anything else. Even though it got nerfed, it's still good.

the next item I get is completely game dependant, if we are doing good and we don't have a jungler, I get the armor over boots, I prefer doing it this way because it gives a chance for your lane partner to outlevel their lane and the jungle gold + experience isn't wasted.

I try not to go back until I have about 1100+ gold, that way, you can get your philo stone, armor, and at least 1 sight ward (if not, get health pots) then head off to the jungle. If you have to go back earlier for some reason and can't afford the chain vest, get boots and about 4 health pots then. In the jungle go: golem > wolves > ghouls (or whatever they're called)> lizard > other golems then bot lane to gank. if you decide not to jungle,go back to your lane and farm, with boots and wards instead of the chain vest.

You want your sunfire cape finished by now (around level 10-12) but if your are dying a lot, get an Aegis of the Legion, this is a great early game item, but I don't like having it (mostly because it means I'm doing bad, which kills my confidence). If their team has a lot of ad, get glacial shroud and turn it into a frozen heart, then thornmail. otherwise I tend to go for force of nature, it gives you nice health regen, you never have to go back again unless you need items and if you have your team around, you can low health bait them like a boss (he's really durable and when dps doodz are attacking them, the enemy will usually not focus you, unless they're smart). Don't stick to a lane alone on low health though, that's just asking to be killed. Warden's mail is also a pretty good item, I've started getting it sometimes instead of frozen heart if the rest of the team doesn't get the buffs. However, if you're getting cc'd and killed a lot (deaths don't really matter if you team ends up pwning the rest of them after you die, but if you die alone, not achieving a thing then it's a problem) turn your philo stone into a Eleisa's miracle here, otherwise do it after your abyssal sceptre.

Next item you want is an Abyssal sceptre, gives you MR, AP and decreases the MR of nearby opponents, epic! if my team is doing really well, I tend to think **** that to the frozen heart/force of nature and get this first. If you didn't get the force of nature, get the MR item first, otherwise get the rod.

Eleisa's miracle here if you haven't got it already.

At this point in the game, you've usually won or lost, but if it's still going, get deathcaps next until your inventory is full, if you have force of nature, and nobody is getting buffs still, you can sell the Eleisa's Miracle for another deathcap, I only do this for the lols when I don't care anymore, but it works well even if you have only one deathcap.

General stuff: Make sure the jungles are as empty as possible throughout the game, get the dragon and nashor as soon as you can (can do dragon about level 7 with another guy, otherwise wait till about level 10-11) and whenever they reset. Remember to plant wards as much as possible and get the rest of your team to as well if they aren't. Also, think before blindly following instructions, don't be off killing doodz in the jungle while you team is getting owned because they don't have their favourite Amumu with them.

Team fights: you want to pop your ult and let the rest of you team kill them all as you have despair and are spamming E. Try getting as much of them as you can in your ult, but don't delay it otherwise you and your team will die. Even if you catch 2 guys in it, it means the other team will either have to back off or do a 3v5 which. With small 2v2 fights and stuff, you want to pop w, bandage toss in, spam e while you wait for your other ally to be in position, then ult, unless they're getting away, then ult earlier. As you get more used to the guy, you can tell when they are scared of you, use this to your advantage, you can easily do 1v2's and maybe even 1v3's (only done this a few times) when they are concentrating on running away instead of killing you.

I don't like doing this from the start because you have to spend money on items that aren't very useful, and you also can't have your second summoner spell because you have to have smite, which isn't helpful at all later on because you can kill everything pretty easily without using smite.
I use elixr of fortitude because it's cheaper than cloth armor and I can't afford the health quints required to kill the golem by myself yet.

That's it, I will be improving it as I get better with Amumu and as I learn how to build a guide properly (sorry about this)

Play with friends as much as possible, it's so much easier when you know how the rest of your team plays and they know how you play as well (never lost a game when playing with my 4 LoL mates :D)

Remember to have fun with it and don't take **** from people when they insult you, confidence helps a lot with your gameplay and you don't make foolish mistakes when you think you're the king of the world, but don't be overly confident, you aren't invincible (it can seem like it sometimes) it's an amazing feeling you get when the enemy team says you're epic.

Hope this guide helped you, comment and rate it so I can make it better, any suggestions at all are helpful.
Thanks guys!