What version of Oracle are you using?
If it's 12 then there is an IDENTITY type that will handle the id incrementing for you.
If it's earlier, then I would hope you had a SEQUENCE for that ID which you use on INSERT.
So your INSERT would be something like:
Now, you can then stick that in a
PL/SQL loop to create 50 of them.
You might even be able to come up with a way of not hardcoding the 50, but I wouldn't worry too much about that!