That is fine for a game the first time you play it, ot when it is a complete game, but when you have to replay certain parts, then there is no point. Besides, if you only wanted the extra money, you can play the cheat version, and still do everything.
Are you trying to do Jenny and Debbie at the same time? If you have no done enough of Debbie's route yet, it will break Jenny's. You need to do Debbie first, then do Jenny, then you can do Diane. After that, Erik, then the French Teacher, then Science, Mia, and then Art and/or Music. Roxxy can be any time, though I would go after French class for it to make more sense.