which is to be done first sound amplification or noise reduction

Actually, that doesn't follow... if you amplify the signal, then yes, the noise will be amplified too - but the dynamic range will remain the same. Noise reduction will have the effect of increasing the dynamic range (the noise floor will be lower) and amplifying the signal afterwards will retain that; noise is a relative issue, not an absolute one.

Amplification doesn't affect noise as such - it's only about the signal level. The way that NR works means that it doesn't really matter whether you've amplified the signal first or not - except for one thing: if the signal is really quiet, then because you will have had to turn up the volume to listen to it, you'll hear additional system noise as well that isn't part of the signal. So your best bet, in terms of overall performance is to normalize your signal to about -1dB and then do the NR. The results will be the same, but it will be easier to monitor.