1st level: Shapeshifting: You can change shape to assume the shape of normal-sized animals, that don't have a swim or fly speed, no more than 1/2 your level CR. You can change shape level + Wisdom modifier times per day. Each change is individual, i.e. you must use one of your "shifts" to turn into the animal and then another "shift" to turn yourself back into you. You must return to your normal shape before you can assume another animal. You get the healing yourself thing, however that works in 5e.
3rd level: You can now turn yourself into animals with a swim or fly speed.
5th: You can now transform only part of yourself to take on nature abilities or weaponry and alter your physical appearance, as per the Alter Self spell.
7th: You can now use a "shift" to give yourself the appearance of a humanoid, no more than half to half-again the size of your normal shape, and taking on the physical characteristics normal for the chosen humanoid.
9th: You can now change from one shape, directly, to another (without returning to your normal form).
Once you get over 10th level...I dunno, add in giant versions of animals?
Over 15th I'd throw in the elemental forms.
That should do it.
ncG1vNJzZmivp6x7prrWqKmlnF6kv6h706GpnpmUqHy0tMCpnKygmZvBqrrGZpinnF2ptaZ5w6usopxdmLmiv9Jna3FraWiCcA%3D%3D