Just startting the thread.
Always use Blue Potions. Sure they cost 1000g for the +9, but the goal is to win and get the +5 to an attribute, easily worth more than 5000g even at level 20, far more later, so it is a smart investment.
Try to have your health close to 100%
It is hard to pick the ancestor you'll battle now because they tweaked the system to random selection, but you can still check to see which ancestors are possible opponants by refreshing the page a few times before you drink the potion when prepping to battle. If there are 2 or more ancestors who have beaten you/clan mates - hold off a few mintues and try again.