$1 on red
$1 on black

wheel spins: lands on black =>you win $2

$2 on red
$1 on black

wheel spins: lands on black=> you win $2

$4 on red
$1 on black

wheel spins: lands on red=> you win $8

$1 on red
$2 on black

wheel spins: lands on black => you win $4

you've wagered a total of $13 and won a total of $16

Net: $3
And you spun 3 times (discounting the first one which will be breakeven.) So you're EV should be $1 per spin.