You are right that works aren't what gets you in to heaven. It is Jesus sacrifice for you that does.. when you entrusted your salvation with Him.
Good works are a response you take because of what He has done for you. It is the reasonable service considering His great love for us.
Someone who doesn't build on their faith.. has the place in heaven.. but does not receive the same rewards as someone who has built on their faith and pursued Jesus.
(1Co 3:11) For other foundation can no man lay than that is laid, which is Jesus Christ. - This is the foundation as saved person has at salvation
(1Co 3:12) Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble;
(1Co 3:13) Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is. - saved people will stand before Jesus - not to judge heaven or hell.. but to judge there place in heaven
(1Co 3:14) If any man's work abide which he hath built thereupon, he shall receive a reward. - faithful being rewarded
(1Co 3:15) If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire. - saved person who went there own way being judged.. but still a place in heaven.. still saved.
Some more on this: Jesus speaking to saved people:
(John 14:1) Let not your heart be troubled: ye believe in God, believe also in me.
(John 14:2) In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you.
(John 14:3) And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.
More on rewards:
(Rev 22:12) And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be.
(Rev 22:13) I am Alpha and Omega, the beginning and the end, the first and the last.
(Rev 22:14) Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city. - the city is the heavenly Jerusalem.. the local city of heaven
(Rev 22:15) For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie. -Outside the gates of the heavenly city are saved who have been unfaithful. They are not in hell.. they are not in purgatory.. they are outside the gates of the heavenly Jerusalem city.. but still in heaven
So what exactly the rewards are? I don't know.. but the key thing here is..
works have no bearing on entrance to heaven.. only what place Jesus will give us in His rooms..