How far should the source be, for the gravitation waves to be visible on Earth? If I understand it well enough, gravitational waves cause ripples in the space-time fabric. To our eyes, that would look like those rippling-effects on amateur videos. 

Where does a source have to be, in order for the effects of gravitational waves to be visible, here, on Earth.
The waves pass by at the speed of light. So you you would'nt see ripples, they would pass too fast, and remember the waves would be passing through you too. The wavelength was (relativly) long about 3000km. The wave doesn't pass you, you are inside the wave.
The amplitude of the waves detected by LIGO was small, one part in $10^{21}$, Now while the intensity of the waves follows an inverse square law, because intensity is proportional to amplitude squared, the amplitude is inversely proportional to distance from source.
We are familiar with strains that are one part in 1000, that is a variation of one millimetre for every metre. To get that we would have to be a lot closer to the source, $10^{18}$ times closer. Since the black holes were about 1 billion light years distant, to get a strain of 1 part in 1000, the black hole merger would have to be about 10000km away
Now if you are 10000km from a merging pair of 30 solar mass black holes, the strain of gravitational radiation is the least of your problems. If it is any consolation, your problems won't lost long.