Joakim Sundén, in his talk You can do better than the Spotify Model talks about the concept of “Minimum viable agility” (around 27m):

Every time you have a new team, or a team splits, they kind of have to reinvent the wheel about on how we should be work. Maybe we should do it that we have this “Minimum viable agility” and that’s what you start with. Feel free to opt out, but people shouldn’t have to opt-in all the time."

I see the same all the time for startups, too, not just new teams in large companies (like Spotify).

So what does Minimum viable agility look like? If you have no other guide (such as another team you can copy), a simple answer is to choose from the well-established, existing agile methodologies. Scrum and XP are probably a great starting point. They’re both well documented, so you won’t have to spend much time bikeshedding on how to do things.

Just don’t get stuck thinking that you have to follow the Scrum and XP “rules” rigidly. Do what works for you.