A spoiler-light order for the main story plus useful side quests, with prerequisites and a short explanation of what each quest expects you to do.
Main-story arc ordering follows Digital Extremes' official Quest Guide. Exact Star Chart/Junction requirements can change, so check the Codex if a quest is not yet available.
Arc 1 — Awakening
Build your footing in the Origin System.
Arc 2 — The War Within Saga
The central Tenno story begins to open up.
Arc 3 — The New War Saga
Prepare your Railjack, Operator/Drifter and story progression.