What chapters does Re:ZERO -Starting Life in Another World- Season 1 (Arcs 1-3) cover?

Re:ZERO -Starting Life in Another World- Season 1 (Arcs 1-3) (Episodes 1-25) covers manga chapters Light novel vol. 1-9, which are found in volumes LN 1-9.

Where should I start reading after Re:ZERO -Starting Life in Another World- Season 1 (Arcs 1-3)?

After Season 1 (Arcs 1-3), the story continues in Season 2 (Arc 4) which covers chapters Light novel vol. 10-15. Or you can read ahead from the manga.