Johann Baptist Cramer's "60 Studies selected by Bülow" are foundational technical exercises. Hans von Bülow's selection highlights studies particularly effective for developing virtuosity and musicality.
Focus on clean articulation and rhythmic accuracy.
60 Studies selected by Bülow is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
60 Studies selected by Bülow is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.