This will be the first movie following IFW, and if we keep it in real time means that Pete would in college. He's now 16 and this movie seems to immediately follow CW which could put it in the 2016-2017 timeline so 2019 would mean he's 19.
Maybe following IFW he prepares for college, then we intro Dr. Conners (not Lizard), if they're bringing in MJ or Gwen this would be the time. Also if they plan on using Harry this would be the place to introduce him as Pete's college roommate. Could see Silvermane working with Conners. Throw in some low level thugs, or Hobgoblin acting on the crime syndicates behalf. It would also be a decent time to try out Black Cat. King Pin would be awesome here at the end as a flash of what's to come.
I'd say they get one more with Pete as an undergrad or he could go for a masters. Kraven and some of the more bio engineered villians would come in as Pete gets his masters meaning Doc Ock etc. This is also where I'd put Green Goblin.
If there's a 4th that's when you bring in Venom. Maybe Pete is a PhD candidate.