I think it depends on how much of his story they're willing to cover in non-Spidey movies.
Personally, I'd make sure he had the Symbiote and fought with it in Infinity War Part 2. Showing Spidey fight in the melee with Thor/Hulk/Thanos really lets him be badass and show a level of strength he might not be able to use on one of his own villains (without killing them, at least).
Then, two of the 2020 movies are Sony, kinda get their own "mini MCU" thing going on.
First one is Spider-Man Homecoming 2. (Ideally they'll just give the sequel a new subtitle, so I don't have to call it that to distinguish it from Spidey 2 and Amazing Spidey 2) Going by the MCU's "movies take place in roughly real time" thing, SMH2 should put Peter Parker as a college freshman. At this point he's done his heavy lifting with the symbiote, so we open the movie with him going overboard (too violent due to the symbiote's influence), and choosing to get rid of it. Same scene, he encounters Flash Thompson, just home from his time in the army (due to permanent injury). Flash helps him get rid of the symbiote. Spidey goes on to adapt, start to recover Spidey's reputation from the harsh actions Symbiote Spidey was witnessed committing, and get his feet back under him in time to face off against the villain (bonus points if it's the same guy who he beat down as Symbiote Spidey). White text on black screen "Spider-Man and the Venom Symbiote will return..." or something.
Second movie is Venom. Show more of what happened to Flash Thompson (he's our protagonist, after all), maybe show how assisting Spidey helped him find purpose after being injured in the military. Then he finds out he's got the symbiote. Healed, stronger, faster, better, etc. Turns out Eddie Brock got part of the symbiote too (then a sub plot of how either it recovers and becomes two symbiotes, or how one of them needs to reclaim the missing piece from the other, whichever works best for their future movie plans). Flash goes to Spidey for help, Eddie starts terrorizing people, Spidey goes to intervene, Eddie kicks his ass (since Spidey Senses don't respond to Venom), Flash saves him. Flash learns Spidey = Peter, and struggles to master the symbiote well enough to fight Eddie while Peter recovers. End with a straight up Agent Venom vs Venom fight.
Personally I'd like to do Venom first, and focus on the removal of the symbiote from Flash's perspective, but then you'd end up doing the entire Symbiote arc BETWEEN Spidey movies, and that wouldn't be great. And doing Spidey 2 first gives you more time to focus on the aftermath of him separating from the symbiote, and lets you cover things like Peter in college, The Bugle/JJJ, and Flash coming home, so there's less to set up in Venom. You could save Eddie for the Venom movie (showing him growing to hate Peter/Spidey while you show details of Flash's accident/injury), or you could set up Eddie as a side character in SMH2.
I could theorize past that (do Smythe and his Spider Slayers as the villain Symbiote Spidey beats down, maybe Spidey is even the reason he's in a wheelchair, Oscrop either funds a full massive Spider Slayer robot or the research on a sample of the symbiote Smythe's bot acquired to lead towards his "Ultimate Spider Slayer" form if that can be pulled off in a movie, and later Spidey can adapt the robots to Spider Tracers/Drones to track Eddie/Venom), but I think that would be solid towards building a Spidey-Verse (I'd like Sony to have a sort of "mini MCU", with 2-3 heroes in their own movies all sort of linked together, tighter than people like Iron Man and Captain America in the MCU, but not as big as the Avengers phases, you know?), and this would have them 3 movies in, with 2 protagonists. Then they could develop adjacent, like a Venom 2 building towards Carnage while Spidey's own movies are going towards Osborn and/or Sinister Six, or something like that.