Assuming that the first measurement is x likes, the second is y likes,
Then the estimate of the natural logarithm of the growth is given by
log(y / x) with an error estimate of sqrt(1 / x + 1 / y)
But since you are interested in the conservative estimate of the growth, you should use something like ~ 5% confidence interval. So I would recommend ranking your dataset using the folllowing function. log(y / x) - 2 * sqrt(1 / x + 1 / y)
For example:
growth from 1 to 10 will get the score of 0.2
growth from 100 to 400 will get the score of 1.16
growth from 10000 to 15000 will get the score of 0.38
One of the important properties of this estimator will be that the growth from say 10000 to 100000 will be ranked higher than the grown from 1000 to 10000, which in turn will be ranked higher than the grown from 100 to 1000 etc...