Hey welcome. Too many mods to do just do one first. Do at least 2-4 simultaneously. Whether you realize it now or not, you are going to want to take this thing off road. So I say sliders, is your first step. Then lift, then tires, then skid plates, UCAs, storage compartments, Orangeboxx PSDs, CB, rear lower links, front bumper, rear bumper, roof rack, and so on and so on.
Metal-tech is a group company and supporter of the FJ community.
Metal-Tech
Toytec is another good company. They offer a 10% discount to FJ Forum members.
ToyTec
TRDParts4U
TRDParts4U
Bubdbuilt, a personal favorite of mine. Awesome guy and family man. NC company as well.
Budbuilt.com
I am sure other people here will chime in and give you more input.