I'm about 100 piett shards and g12 and relics on 4 more characters away from papa palps. So around the same area.
Most of the characters for GL luke don't need hard node farming. Just chewpio and mon mothra for me. So I'll probably farm both of those with one refresh each and still farm cara dune too. I've been farming mando and greef on fleet anyway and will continue to do so.
I plan on starting gearing jml requirements when I'm done with papa palps starting with the most useful (cos, raid han, chewie, ect...)
I don't think farming the shards for the mando characters will interfere all that much. Whether you want to gear them now or not is up to you. The real questions are how high the gear needs to be for a legendary and how useful the team over all will be.
I will probably try and get them all to at least 5 star and gear 7 or 8 but I'm probably not going much higher without more information.