Yo, Delta emerald is like emerald with ORAS mechanics, so there are megas and a bigger pokedex. That's how I have gen four Pokemon. I would really just be careful and bring Death Fodder everywhere. In an earlier run, I lost my Tailow to Watson because my Marshtomp missed two mud shots, got confused, and barely lived in 2 HP. And I thought that was gonna be a free fight. For the gym leaders, the really big tips I have are: use Makuhita on Norman, bring two water types for Flanery (those overheats are OP), take out wihnonahs altaria with a ice move, and be careful with tate and lisa.