My database has a lot of default users such as tracesvr, scott, Blake,adams, clark, jones, etc,
that I didnt really create.
All of them have their default tablespace as system.
DO i really need them or are they just occupying space, because my system table space is used upto 96%
Scott, Blake, Adams, Clark, Jones (and a few tables like EMP, DEPT, SALGRADE) are created by a script included in Oracle. They're from demonstration purpose only, the Oracle's training exercises are based on these users/tables. Probably you executed the script during installation.