In what order should I install roofing, gutters, and attic insulation?
You want to do the roof before the gutters. Gutters attach to the roof decking and/or the fascia so if you did them first, they'd have to be removed. If the additional venting you mentioned is going to be installed on the roof, turbines, etc., they go in afterwards or possibly along with the new roof. If the venting will be installed in the eave with soffits, that can be done afterwards. Last but not least, the insulation goes in after everything else is complete