If you want to get the SB and go cheap as possible; order the SB and possibly an adaptor for your atty preference.  As I recall, you already have a 3.7 volts PV; therefore, at least initially, just get a charger and 
batteries (COMBO KIT: 6 RCR123A 3.0V 750MAH LIFEPO4 RECHARGEABLE 
batteries WITH A SMART CHARGER -$26.99) at the Battery Junction (someone else posted the link).  These batteries will give you the opportunity to vape at 6 volts.  In the future you could always purchase the 3.7 volt batteries /charger for the SB.  As for the “1x Green Case +$1.99”, this is just a plastic little box to hold your extra batteries.  I purchased one since it was only $1.99 and it does come in useful to carry your batteries, but it is not needed.  The 3 volts batteries also fit in this box.
Summery:
SB and possibly an atty adaptor
Charger and batteries from Battery Junction
This is all you really need to start 
vaping at 6 volts.