Start with easy, cheap animals (that don't get scared easily and are cheap to feed). Peafowls and warthogs are good examples (and peafowl have the extra plus of guests beeing able to visit the habitat). Once you have reserched animal fences so that you have the one way glass, you can add other cheap to keep animals like Red pandas, Tortoises, Flamingos, gazelles etc. You should wait with harder to keep animals like carnivorus until you have a good income and add them slowly. (and if you add animals like crocks or nile monitors, do NOT forget to use contraseptives, cus they breed like bunnys, same goes for the aldabra tortoises).