This is interesting so i just wrote the code. Not enough testing though, but i hope it works. The difficult parts are checking here and there, so the game cannot be cheated easily, also prevent bot got flooded.

Code:
on *:text:*:#:bet # $nick $1-
on *:nick:bet_ $nick $newnick

alias bet {
  noop $regex($3,/^!((?:new|won)?bet)/)
  var %r $regml(1)
  if $istok(newbet wonbet,%r,32) && $2 !isop $1 { return }
  if %r == newbet {
    if %bet.q { .notice $2 Bet was already opened | return }
    if !$4 || $numtok($4-,58) != 2 { .notice $2 command: !newbet <question> : <option1>,<option2>,<option3>,etc | return }
    msg $1 [BET OPENED] $4- - Use: !bet <option> to set your bet.    
    set -e %bet.q $gettok($4-,1,58)
    noop $regex($gettok($4-,2,58),/(\S.+$)/iS)
    var %re /((:?\s+)?,(:?\s+)?)/giS
    set -e %bet.a $regsubex($regml(1),%re,$chr(44))
  }
  if %r == bet {
    if !%bet.q { return }
    if $wildtok(%bet.user,$+($2,*),1,215) { 
      if !$istok(%bet.twice,$2,32) {
        .notice $2 You cant bet twice! 
        set -e %bet.twice $addtok(%bet.twice,$2,32)
      }
      return
    }
    if !$4 {
      if !$istok(%bet.warned,$2,32) || $2 isop $1 { 
        .notice $2 [BET] %bet.q : %bet.a - Use: !bet <option> to set your bet. 
        set -e %bet.warned $addtok(%bet.warned,$2,32) 
      }
      return
    }
    if !$istok(%bet.a,$4-,44) { 
      if !$istok(%bet.invalid,$2,32) { 
        .notice $2 Valid options are: %bet.a 
        set -e %bet.invalid $addtok(%bet.invalid,$2,32) 
      } 
      return
    }
    if !$wildtok(%bet.user,$+($2,*),1,215) {
      set -e %bet.user $addtok(%bet.user,$2 $4-,215)
      msg $1 $+($2,'s) bet is $4-
    }
  }
  if %r == wonbet {
    if !%bet.q { .notice $2 There is no BET yet. | return }
    if !$4 { .notice $2 command: !wonbet <option> | return }
    if !$istok(%bet.a,$4-,44) { .notice $2 Valid options are: %bet.a | return }
    var %i 1
    while $wildtok(%bet.user,$+(*,$4-),%i,215) {
      var %win %win $iif($gettok($v1,1,32) ison $1,$v1)
      inc %i
    }
    msg $1 [BET CLOSED] $+(<,$4-,>) was the winning option! Winners are: %win - good luck for all others on the next bet!
    unset %bet.*
  }
}

alias bet_ {
  if %bet.q {
    set -e %bet.twice $reptok(%bet.twice,$1,$2,1,32)
    set -e %bet.warned $reptok(%bet.warned,$1,$2,1,32)
    set -e %bet.invalid $reptok(%bet.invalid,$1,$2,1,32)
    if $wildtok(%bet.user,$+($1,*),1,215) {
      set -e %bet.user $reptok(%bet.user,$v1,$2 $gettok($v1,2-,32),215)
    }
  }
}