My personal preference is to start with Implementation test, Support is for HP service engineers. But if you have done much of implementations and confident then support test is not bad too.
I will suggest you to go and register at
www.hp.com/certification website and then register for certifications. With new look HP portal has lots of problem (and I am a victim too) but gives you lots of new features to track your certification path. The very basic to start with would be AIS-StorageWorks and once you are registered for the certification path it will tell you all pre-requisites and optional tests.
Good luck with your studies.