Even if you do not want to contribute on a large scale and become a leading environmentalist, there is always the possibility to do your small role of the following things below:
Animals have feelings too. If you are going to keep them locked up in tiny cages where they can barely even move... well how would you feel? Some animals are bred in captivity, for example various lizards, cats or dogs; some snakes too. Because they are captive, that doesn't mean they can be treated like 'convicts'. Some pet shops are like jails, some are like relaxing luxury hotels. You want to aim for the luxury hotels while getting an captive animal, although make sure you know where the sellers get them from; as there are puppy mills, kitten mills etc. where they treat them like factory products where the parents are the machines which only need an occasional 'oil' to keep them working (they're underfed).