I highly recommend using the "Compare Mates" feature for successful breeding. Just looking at the genetic stats and putting the best two animals together in one habitat may not work so well.
For example, breeding with two golden rated animals may result in lower-ranked offspring, as the genetics of these animals are "too good". You can get better genetic results if you breed with a golden and a silver animal (or even a bronze one).
When you have an animal with a low size-gene e.g., try to get a breeding partner with a high size-gene to overcome it.
On the animal market, you can (almost) completely ignore the immunity gene. It's just an offspring of inbreeding, but you have a different bloodline in your zoo, or you'll be adding another animal from the market anyway. Diseases shouln't be a problem in your zoo, and it may happen that even an animal with 0% immunity will already have offspring with 100% immunity in the next generation. But animals with a red immunity bar are often underprized because people think: oh no, that's a bad animal - No, it's not !
just get the right breeding partner for that animal. Pay more attention to the infertility warning when comparing mates. There are many animals on the market that are already infertile.
Yes, you need at least two habitats for your pandas. You may want to add another one for the offspring in the future, depending on how much you want to breed. Then you have two breeding pairs in their own habitats and if you are lucky, you will get a highly rated male and female from each of the pairs to breed a third bloodline in this enclosure. From now on you can sell the next offsprings for CCs. Once your parents get older, you can move three (preferably golden rated) young animals to your Trade Center, depending on which gender is cheaper to buy. Mostly the males are much cheaper so you want to keep the females, but that can vary. If the parents have become infertile or have died, you can put your own offspring in each habitat again and add three new (silver rated) males, for example. Still, use the "Compare Mates" feature to sort the best pairs out - the differences can be huge.