Well... I know what you're thinkin: noob; build fail; shoot yourself...
I tell you one thing... Karma is a support char and even if we try to build it to kill a lot it is always a support and it's needed to help teamfights...
Now i ask you something... How can you support if you're the 1st dying?
There are lots of builds that say to you choose ability power... why? you'll be the low hp... everyone will aim you and you won't support anything...

If you want to be a good Karma read a little more to know my reasons to use this build and even if you're not interested you should read and you might found some ideas!!!

This build consists in having the best of both worlds: Tank and Caster... I chose some of the best Items of each class so Karma can hold a lot of damage and suport a lot!!!

As everyone knows since karma is support it needs ability power and Doran's Ring is the perfect starting item that you'll keep during some time in game (i talk about it later)...

Following it you'll need Ionian Boots of Lucidity to reduce cooldowns since Mantra is the base of this char and you'll need it always ready...

Now Warmog's Armor... This armor is just perfect... at lvl 18 you'll have nearly 3500 hp and you're hp regen will be great!!! This armor is not a fail... With all this hp everyone will try to kill the casters that are usually the lowest hp and you are able to support you're team more than 3sec since you'll be considered a "tank"!!!

Then comes Rabadon's Deathcap... It's a great item since it helps Warmog's Armor to stack more hp and regen... It also gives you a lot of ability power that you really need since you have been only using Doran's Ring (at this time of the game you can sell Doran's Ring, but you got to keep it until here to have a reaseonable ability power).

Spell Vamp helps to keep you alive and it fits great in almost all (or even all) casters, so next you can buy Will of the Ancients and you'll survive much more because all spells you cast will regen a little of you hp and since your 1st skill heals too it's just amazing!!!

At this time of the game you should start to worry about cooldowns since teamfights are everywhere and your support can't help everyone as fast as they need... so you can buy a Spirit Visage to reduce your cooldowns and even making you harder to take down since it gives you more hp and magic resist that you need so much on teamfights!!!

To finish and to make your spells a little stronger you can buy Zhonya's Hourglass cause it gives you 100 ability power and you'll be over 350 that is not perfect but it's perfect... if you had 600 your skills would be surely powerful but you'd die before using them that's why this equilibrium is good... This item is also good for it's passive.

Runes will solve lots of this char's problems...

Starting for the red ones... I've chosen magic penetration since the red ones give more than the others and it is very helpful cause you will miss a little ability power at the beggining!

For the blue ones I've chosen ability power cause this ones give more than the others and it'll help you a lot since you got to hold without buying ability power during some time!

For the yellow ones I've chosen the cooldown reduction... It doesn't gives much but since Mantra is very important in this char it is great to have it always ready... I let this in disadvantage because you need to have stronger skills in the beggining that you don't have much ability power!

For the big ones I've chosen with the same effects as those 3 before... I did this cause you can chose what are the best for you... You can use 1 of each or you can chose, for example, all ability power cause you miss ability power or you can chose cooldowns cause you need Mantra more often or so on... Be creative!!!

About masteries... All support chars need Utility masteries... The ones i chose are probably the best but you can change something kinda: Instead of Perserverance you can chose Good Hands or instead of Greed and Meditation you can chose Utility Mastery (I don't recommend this one cause karma don't needs much jungle but if you like to have the "Mana Buff" it is also a good choice)...

Then you can spends all points in offense since defense are for tanks and since this build don't grants you as much power as you wish... so you can chose all masteries until you reach Archaic Knowledge to give you more magic penetration.

The best thing you do it is to start for the 1st one then the 3rd one and finally the 2nd one...
I recommend that you evolue the 1st one until the end because it's almost you're only attacking skill and because it heals you (heals only with Mantra)... Then I recommend the 3rd because it keeps you even more alive and saves your allys lots of times if you use it right because it gives armor and magic resist (and attack everyone around if used with Mantra).
In the end you can chose the 2nd one because it slows your target and gives you more speed if it is an enemy and speeds both if it is an ally. Every enemy in the middle of it gets slowed and recieves damage. You can give it to an ally and make a low kick to your enemys ^^

With this summoner spells you won't even have to run.
Immagine this: You have been healing and protecting your allys and you are out of mana so you use clarity and you continue... since you can heal yourself and the others you don't need to go back and since you have clarity when you're low mana you don't need to go back too...
Then i chose ingnite... I could have chosen exaust but the 2nd skill works like it, more or less, so ingnite is more useful... you don't have much ability power but you can use ingnite to help you damaging your target!

As soon as i can i will post a video of me playing *.* and you can see what sort of things Karma can do... even being a support Karma can be a great char and even if you don't kill much you can be a big trouble to your enemys and you can help a lot your allys to get feeded

Karma is needed in a lane with a good tank or a good char dps (damage per second)... You can give him protection so he can reach near the enemys and you can heal him... you earn some assists. Don't worry about not killing... a good score for a support consists in assists and these also give you money.
Karma needs no jungle... you can go sometimes to the Big Golem to get "Mana Buff" that is important if you don't want to be always recalling... The best way to farm is to kill minions!

Remember:

Karma is support if you want or if you don't so it won't be as strong as Ryze, for example. If you want to be as strong as one go on and make an ability power build but then cry that you score was negative... Karma is char to assist... If you like to kill this is not you're char for sure... Karma needs to be there helping to feed the others and getting the assists and this won't happen if you are the 1st dying... This is what makes this build so good... You're the last attacked and you can support during more time!!!

If you don't belive how great this build can be try for yourself! my best score with this build was 12/6/27 which is very good since it is a support! If you think you can do better with other builds it's fine but don't quite trying this one even if it is against bots!!!