I just bought one and putting it together. What is the best standalone or the options. I have for the standalone and also what injectors?

 

Standalones
AEM v1, v2, or infinity
Haltech (not sure models)
Motec (expensive)
Hondata Kpro or flashpro depending on the year of your vehicle
I've seen one s2000 on facebook using Pro EFI but that would probably also be expensive.

Injector sizing depends on your goals and what fuel you're running. Take your pick from the manufacturers below.
DW
Injector Dynamics
Fuel Injector Clinic
Fuel Injector Development

I may be missing some others but those are most of the major players for EMS and injectors. I've used FIC and ID and have had great success with them.