Start with boots. If your existing pair don't fit, get some that do.
Then move onto bindings, do they fit your boots ok?
If they do and they're on a board, ride it!
Have a bash at riding your option 160. If that's what you rode as a grom then it'll be fine now.
I'd try not to spend a ton on new gear straight away, as you ride you'll break or wear out your old gear and figure out pretty quick what you'll actually need.
You'll figure out what kind of riding you like best in the process too, this dictate what kind of gear you want... you'd probably be just guessing if you drop bux on everything before the season even starts...
Just my 2cents!