You asked
What lenses should I buy for the canon eos 850d?
For an everyday kit on the 850D, I'd start with the Canon EF-S 18-55mm f/4-5.6 IS STM. It's light, cheap, and its stabilisation helps, since the body has none. The first camera guide makes the same point: the money goes further in lenses than in bodies.
If you want more reach for wildlife or sport, add the Canon EF-S 55-250mm f/4-5.6 IS STM.
For a stronger, all-round upgrade, the Canon EF-S 17-55mm f/2.8 IS USM gives you a bright constant aperture for portraits and low light. It costs considerably more, so buy it once the cheaper kit lens feels limiting.
Written by Claude from this site's pages.