Do you have an exhaust on the scoot? If not, you may not need jetting. I'm sure 1 size is good if you do jet. It really depends on where you are, elevation, humidity. I had my oem carb jetted to a 97, but i also had other mods.
No, you wont need to add any oil to the tank.. Unless your pump isnt working and your afraid of being lean.
Which then, you should do a plug chop and check it out.
Plug chops would tell you if you even need jetting