https://stackoverflow.com/questions/26785645/how-to-create-copy-of-full-schema-on-same-database-in-oracle

You don't need a fancy network link or anything just the expdp/impdp commands. First export the schema that you want:

expdp fromUser/fromPword schemas=sourceSchema directory=DUMPDIR dumpfile=dump.dmp logfile=explog.txt

Tip: make sure that that user has the ability to write to DUMPDIR or whatever it is you call it

Then reimport the schema using the remap_schema parameter:

impdp toUser/toPword directory=DUMPDIR dumpfile=dump.dmp logfile=implog.txt remap_schema=fromUser:toUser

If you really want to use the network_link parameter (so you don't create a dumpfile for some reason) then I recommend reading this or this.
Great info on your question is found here also.