I just use the whole map as a place to train gathering. When training an adult, I skip the items that a kid can gather and use those to train the kids. I focus on one adult and one kid at a time, until the adult is a master and the kid is either adept or an adult. I gather everything, not just what I need in the moment.

I'll admit, training healing is hard. I watch videos for lavastones and get a healer necklace, but while I build generalists (masters of FBRG), I am happy with one healer, and I train only one at a time. I have more than that right now. I put an identifier in healers' names and resurrect them when they die.