The very first step is to learn all 60 root position seventh chords: major 7, dominant 7, minor 7, minor 7b5 and diminished 7.
I have a free lesson on this topic here:https://www.jazzpianoonline.com/pages/chords-voicings#five-essential-seventh-chords
Once you have these voicings firmly in your head and hands you can move on to learning how to play them in voicings. (Voicing a chord refers to adding, subtracting and distributing notes to modify a basic chord sound).
The shell voicings that you mention are root based voicings, typically played in the left hand when playing solo piano and most often composed of the root plus the 3rd, or the 5th, or the 7th or the 10th.
Shell voicings are combined with guide tones (3 and 7) played in the right hand under the melody note (whether written or improvised). These two voicing techniques are the basis for the spread voicing technique which is the foundation of playing solo jazz piano.
I have a lesson (requires paid subscription) on spread voicings here: https://www.jazzpianoonline.com/pages/chords-voicings#solo-jazz-piano
In my teaching, I introduce rootless voicings with added tension (the name says it all, voicings without roots but with added tensions, 9, 11 and 13, aka left hand voicings) after the student masters the basic 60 root position seventh chords. The discussion of shell voicings and spread voicings follows rootless voicings.
So to answer your question, there is nothing wrong with introducing shell voicings, guide tones and solo piano playing after the student masters the basic 60 root position chords.