"I think electives at melb are the 'breadth' subjects "
Are you sure? because on sample course plans, electives and breadth studies are shown to be different....
As for picking subjects not offered in 2013, I don't think I have either. I'm planning to do psych. and I've selected compulsory subjects like the mind, brain and behaviour but even those say "no classes available". Perhaps I should just wait a few days? I dunno.
To my understanding... Electives are the non compulsory subjects that are
not breadth. For instance, in commerce, core (compulsory) subjects would be microeconomics which everyone does. But Finance 1 is an elective which some students could choose to do, as it is not compulsory in completion of degree. However, doing physics 1 in commerce is a breadth. I'd assume similar format applies for science and arts.
In your study plan, make sure you are searching for level 1 subjects within the level 1 areas. And that you are not searching for compulsory subjects under elective sections and vice versa. You probably also cannot choose too many electives. Make sure your subject is offered in semester 1 and that you confirm and enrol in the subject after selection. On no. of electives allowed, i'm not sure, best ot check it up with staff.
And timetable as mentioned before doesn't open till later. But it does say 'no classes available' as it does with mine now and last year. Doubt it's an error, and timetable slots should open up in a few days. Don't worry so much.

Enjoy the lagfest that is timetabling on the fourth ^^ .