I would plan on being an F/O for 2-3 years in anything from the Ultra to the Falcon on year 1. After 2 years you will have the option to transition over to NJI to fly the G4 as an F/O if you like.
When you upgrade it will likely be to the Ultra/Encore, the 400XP or the Excel.
You will likely spend your career flying CLASS 1 and CLASS 2 pay airplanes.
You might see a CLASS 3 (DA-2000, G-200) plane in your tenure here if you have several decades to blow.
I am not holding my breath on a CLASS 4 (Falcon7X) in my lifetime with 5 years of seniority.
CLASS 5 (BBJ)?? What is that?? I only see them on static demo occasionally. We have 2.