Kingdom Rush Battles Strategy

I just recently got this game and I keep running into gold dragons and the necromancer tower. I can’t seem to find any counter play to this? I’ve played all the PvE games extensively and enjoyed them very much, including 100%’ing the first 3. Despite this, this strategy seems to be the hardest Kingdom rush obstacle to overcome, I keep swapping my “f2p” deck around but nothing seems to help.