Get a 1.0mm tip (it probably comes with this size) and a 1.6mm tip. Consider 0.8mm and 1.3mm tips as well. Get the cleaning poker for the appropriate sizes too.
Consider getting the cleaning drill bits for sizes you use as well. I don't have the drill bits, and can still clean out the tips effectively. Drill would make it a lot easier.
Get a pack of extra ceramic filters. These go pretty fast and is most used consumable item for this gun. Make sure to get the big ones. There is two sizes of filters, you want the larger (thicker) ones.
The metal filters you can clean. I use these for a long time with out replacing. Maybe skip those.
Rubber seals around the solder waste tube need replaced after a good bit of use. The fill tube itself needs replaced after a bit of use as well, you can clean it out pretty well though.