Hello, can anyone explain the utility of using the bot on several exchanges?
I'd say management and separation of funds, plus some exchanges have different pairs. Some users may be verified with Poloniex already, some with Bittrex et. al.
Also what is the utility of using multiple pairs instead of one for the bot?
Much bigger gains? You're 50 times more likely to make trades with the bot if you ran 50 pairs rather than 1 pair. This one should be relatively straightforward.
I have another question : what is the utility of a VPS with gunbot? ?
A VPS should ensure that your bot has the chance to run 24/7.
Do i have to change setting every day ?
No.