i suggest you add all the live rock you intend to, before adding additional livestock. each time you add live rock, the dead things that are on it will have to rot away, which will cause ammonia to be present in the tank. ammonia is harmful to anything living.
a well established tank can handle the addition of a piece or two of live rock here and there, but a new tank will not be so forgiving.
can you post the model # of the pengiun filter you have? i'm not coming up with anything when i google "penguin 3/1 filter/protein bio wheels".
is this a simple hang on filter, or is there a protein skimmer incorporated somehow?
the "sun glow bulb which is good for fish coral and rocks" is a single bulb you will be installing in a single bulb fixture that came with the tank, correct? this will not sustain any corals. you will need to decide what types of corals you will want to keep, and purchase a new light fixture to meet those corals' requirements.
most corals are photosynthetic, and some need powerful lighting to thrive.
don't get the mandarin until you've had all the rock in the tank, and it's been running stable for atleast 6 months or more. most say a single mandarin requires 100 pounds of live rock in an established tank to survive.
good luck!