I would disagree on the spindle gouge. Most people would go for 40-45° for that one. 30° is usable but would lose its edge faster and you could go steeper than 45° if you chose to.
For a "standard" bowl gouge, I would suggest around 50° and I wouldn't necessarily go with what was on the tool when bought new because some manufacturers put some odd bevel angles on some tools! Much lower and you will find you can't maintain bevel contact on the inside of deeper bowls. Even with 50° you may find you reach that limit - I have one gouge ground at 60° just for the extra deep bowls but initially you won't need that.
As Robbo said, there isn't a right or wrong angle. The bevel angle on the tool (particularly spindle gouges) is the result of the relationship between the lathe height, the height you like to hold the tool and the toolrest height. So if you find whith whatever bevel angle you have chosen that you aren't holding the tool in a comfortable position, adjust the bevel angle to compensate.
You don't necessarily have to grind the tool all the way back to change a bevel angle. If you are going for a steeper bevel, just grind far enough to create a working bevel. There's no need to waste metal and grind it all just for the sake of it. In fact with bowl gouges, I always grind two bevels anyway because they work better that way.