This is a beautiful and lyrical work by Schubert, featuring a flowing adagio and a graceful rondo. The piece is characterized by its warm harmonies and melodic invention, creating an atmosphere of peaceful introspection.
Achieving a beautiful legato line and nuanced dynamic control throughout the arpeggiated passages is essential.
Adagio and Rondo in E (D.506) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 8.
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.
A typical performance of Adagio and Rondo in E (D.506) lasts about 7 minutes.
Adagio and Rondo in E (D.506) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.