Useful, probably. Risky, definitely, especially when it involves money, which gambling does. If you are hiding or masking your IP address because you are playing from a location which is banned or blacklisted, that is immediately a violation of the site's terms and conditions, including Sportsbet.io's. 

As stated in 2.16 under number 2 or Binding Declarations from Sportsbet.io's general terms and conditions, updated late December of last year, the site has the right to detect IP masking, considered a prohibited technique, which is what VPN is basically doing.^[1]

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[1] https://sportsbet.io/help-centre/help-other/help-other-terms-and-conditions/general-terms-conditions