The 16" size really are not all that helpful for anything other than hats and even those can be tough on the Addi's.
I'd say the safest size to get is 32" ones...that way you can fit sweaters, baby blankets. They'd be long for scarves, but you could still do it. You might also consider some 10, 10.5 or 11 in size 24", those are very common for felted bags.
As for needle sizes it really depends on what you enjoy knitting the most. I would need 6, 7, 8, 9, & 10.5s.
Good luck! Addis are terrific! :cheering: