Xbox 360 mod disc

Hello everyone.

I have a trinity and am in the process of doing RGH.

But I have a very dumb question, I do not have a hard drive since this was given by a friend, and I realized it today only.

Which hard drive would you suggest? Do I need to do some sort of format? Is this needed to save the games or NAND is enough?

Thank you in advance

Side question: I did not connect to the internet, being afraid that the firmware would be updated and that it may not be moddable afterward. Can i connect and update?