If you plan to lay off your bet i would make my selections the shortest price horse, sure others will pick it but the lay odds will be in line with it's chances.

If you choose something at 25s it could blow out to 40s on the lay side and you could end up with less, greening up will always cost you, it is hard knowing your selection will return say 2k if it wins but you can only green for $300 to $400 but you know that is a secure bet.