If someone offers to trade you Gold for Karma, don't do it! While Gold sounds more valuable, it isn't, as Karma often has to be purchase using real money! People offering to trade Gold for Karma are often trying to scam you.
There are karma items called Karma Stones which will give you karma just for having them equipped. If you have one equipped you and don't play the game for a couple of weeks you will have a lot of karma. There are different types of Karma Stones, the first one is the weak Karma Stone and it gives you one karma every 12 hours.