If I play a unit with 'When I attack' and have a gear with 'When a friendly unit attacks', can I pick the order in which they're added to the chain?

Ruling: Yes, when multiple triggered abilities trigger simultaneously, the player who controls those abilities selects the order to place them on the chain.

Sequence:

• Both abilities trigger at the same time (when the unit attacks)
• The controlling player chooses which order to place them on the chain