Personally, I would have to say that I agree with Kid Fresh, buying and selling donation items is one quick and easy method to earn large sums of gold without putting forth any real effort, but if you truly desire highly-valued items, it can become a rather costly process.
As for earning gold without utilizing real life funding, I would have to suggest to choose a given forum and then carouse through the plethora of threads within it until you find a thread that interests you, and then simply post a response to the topic and see how others react and or respond to your input, if they ignore your response, then simply move on to another thread and repeat the process. Eventually, by going about in this fashion, you will find others who either support or negate your opinion and by conversing with them you can hold entire conversations and eventually you will forget that there is approximately a minute or so delay in responses and the conversation will seem to flow, resulting in the acquiring of gold while enjoying a good conversation.
And for those introverts out there I suggest to form a small circle of friends and simply try to converse with them on a regular basis over PM's, that way you won't be subject to flaming or anything of the sort and you will continue to make gold while simply talking to your friends.
I do not recommend bumping, though. That practice is generally not cared for by many Gaians, and even though it may allow you to acquire gold while not putting that much effort into your post, it basically defeats the purpose of Gaia.