Help in testing skills

Hello Everyone,
I see lot of qa jobs in the market require either ETL testing skills or SAP
testing skills or Performance testing or Mobile testing skills etc.The
list goes on endless.
As a beginner,it is not possible to gain knowledge in all the various kinds of testing skills.
First question is ,how do we gain experience in all of these as the jobs requires us to have ?
How do we apply to jobs,if the job requirements are so varied and vast ?

Please suggest some ideas how to apply for all jobs (with skills mentioned)and how to prepare for them .
HIghly appreciate your feedback and guidance.