Is there a big range of adjectives to use, at least for me?

Since we’re talking about comprehension of a subject you could say:

A highly adept level of understanding…

An adept level of understanding to work on…

A strong grasp of the concept of…

This work requires an existing level of insight…

It will need a fair degree of expertise to work on…. (where expertise can be modified with ‘a high amount’, ‘a moderate amount’, etc.)