Optimizing dynamic range for acquisition of noisy signal
How much amplification should I apply before the ADC so that I can
  increase my SNR through oversampling.


At least enough to read the noise (including internal noise in the ADC). If the total noise is 100nV then you need to amplify it to 31uV. Then you have a 1 bit sample that can be 'oversampled' to extract a signal which is below the resolution of the ADC. 

This will provide the greatest dynamic range. If you don't need this much this range then amplify the signal until the largest signal + noise is slightly below 1V. Avoid clipping because this will lose information and distort the signal during noise peaks.