Adding to above response, few more things to consider -
1. E-business Suite DBAs are DBAs first, so you should be start with core database admin learning first, rac is not mandatory but will be a plus.
2. E-business Suite DBAs aka Apps DBAs work around multiple technology stacks like OHS, weblogic, oaf, etc and there are differences in every release like ebs r12.1.x and r12.2.x in terms to utilities like patching, etc.
Please go through technical documents if you have time.
you may go through document like this.