I started long ago although had diplomas as programmer analyst for free (stage...) on mainframe then wanting to do some oracle finished by entering unix world... and got a job...

Your best bet now is not only unix knowledge but knowing what is your goal

Pure system? Then be sure to have some C language base ( and a little perl...) and master vi and all common system perf commands AND have a good idea of unix internals, be aware of java stuff and its impact on kernel params and performance/issues...
I have seen many companies trying to deal with web servers nad willing to find someone to tune and maintain the beasts...


Good luck