I don't know why everyone wants Peter to be in high school; personally I would have an older Peter, in his early to mid twenties, graduating from college and balancing not only his superhero life but his personal life from the very beginning. Kind of like Spider-Man 2 in the beginning. Just throw the viewer in there.
The movie should begin with him having witty banter with a common thug robbing a bank and him riffing on the fact he's late for a job interview. The job interview is with Curt Conner at Empire State University. Conner isn't mad that Parker is late because he's used to Parker running a few minutes behind and it gave him time to talk to Norman Osborn as Norman is starting up a research facility with Oscorp and Osborn wants Conner to head up the department. Conner declines causing Osborn to be a little bit irritable as Osborn always get his man but Conner likes teaching.
Parker is also good friends with Norman's son Harry, who manages a coffee shop near the university. He also has a steady girlfriend in Gwen Stacy. His next door neighbor has gone to Hollywood, Mary Jane Watson. (she should only come in at the end of the 2nd movie!)
Essentially it should show the rise of the Green Goblin, a momentary villain in the Lizard but friend in Curt Conner, the steady relationship between Gwen and Peter, Peter's struggle with responsibilities along with Harry's responsibilities as an Osborn.
Key scenes should be Norman's...disapproval of Harry running a coffee shop as it is beneath him. Norman's growing insanity due to a botched break in to Conner's lab exposing him to some off chemical of the super human formula (which also causes Conner to become the Lizard as he is trying to regrow back his arm and is testing and working with the former super human formula that created Cap).
I think in the 2nd movie, Green Goblin is a manipulative force in all of this but is rarely seen on screen. He finds out who Spider - Man really is, and in the end kills not only Gwen Stacy in a scene where she is thrown off a bridge but also his own son, Harry as the Green Goblin (not Norman) believes he is not up to snuff to become the next great Osborn and when sending him to Europe for a 'business' trip, destroys the plane. It's a darker movie but I think at the end, Mary Jane Watson should show up at Gwen's funeral to support Peter and tell him that if he needs anything she'll help him as Gwen was her friend too. Peter also breaks down but it makes him more determined to be Spider - Man. As for the bad guys, I would think Mysterio and another few others should be used as well.