I'm trading with my kid, she's lvl24 I'm lvl37. I'll send her a good iv pokemon (she collets the cute ones but they are terrible to battle with) to help us both out but that just down grade to 1 stars.. how can I keep them at 3 stars and useful when I trade with her?
Just keep trying. Trade lots of random stuff too and sometimes the random stuff ends up lucky and better than you expected and the more luckies you have the more likely you will both be to have a good number of different variety types for raiding different types rather than focusing on trading the big baddies I hope that made sense..plus tanks can be helpful too like blissey snorlax blastoise.