#1 for every single person is the knuckles.
#2 for every single person is a servo.
Those things are junk and MUST be replaced.
Aside from that shocks and turnbuckles are the most essential to anyone that wants to handle well.
Once you can handle well you have to decide if you want to race or go 50mph. If you decide to race you are ready. If you decide to go 50mph you have to replace most of the truck.