Johann Baptist Cramer's '50 Studies selected by Hans von Bülow' are foundational exercises in piano technique, highly regarded for their musicality and effectiveness in developing dexterity and fluency. They bridge the Classical and early Romantic periods in their stylistic focus.
Achieving legato phrasing and clear articulation across a wide range of dynamic and technical demands presents the primary challenge.
50 Studies selected by Hans von Bülow is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
50 Studies selected by Hans von Bülow is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.