Johann Sebastian Bach's '3 Sinfonias,' also known as the 'Inventions,' are pedagogical masterpieces exploring contrapuntal techniques and keyboard facility. They are essential studies for developing independence of hands and intricate musical lines.
Developing clear voice leading and precise finger articulation for each independent melodic line is crucial.
3 Sinfonias is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
3 Sinfonias is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.