You're probably just trying Amumu out to see if he's a good tank in top as he is in the jungle, either that or you were guilted into playing him top after being gifted Emumu from a mystery skin.

Since My Guide Maker was Bugging out, here are the runes here:

3 AP Quints
9 Scaling Magic Resist Glyphs
9 Scaling Armour Seals
9 Magic Penetration Marks

Since this build is primarily leaning towards tankiness over AP the masteries are more for Armour than Damage, of course if you want to be kamikaze Amumu, you can totally switch those up.

Since most top lanes besides you are AD building into an Iceborn Gauntlet is key for your lane sustainability, you will block some damage they throw at you will dealing gradually more as the game continues. From there on, building a Sunfire Cape and Abyssal Scepter are important as they both provide MR and Armour but also provide AP (Scepter) and more AoE damage (Both)
After those three it's your choice on how you want to build, more tank? build more armour and mr than AP. more AP, build more AP oriented items while still keeping tanky items too.

Maxing Despair first is good if you plan on having optimal amounts of AP since it deals percentage health damage to enemy champions, maxing Tantrum second is not necessary but can be helpful more so than Bandage Toss.

Always have teleport, but ignite is more aggressive, if you feel that you aren't going to be able to always be successful in fights, you can switch ignite out for flash.

Pros

Very Tanky Early Game due to Tantrum
Can usually shred through enemy champions health early game
Fairly simple lane clearing

Cons

Can also be squishy to the more dangerous top lane champions
Very mana heavy early game
Does not help much in other lanes until mid-late game