I would estimate this would be around 144 ln. ft if the building has 12" gable end overhangs. The price in our area for 5" seamless K style guttering with 2x3 downspouts is around $4.50 per linear foot, installed. We would use (4) downspouts on something like that.
The ribs in the metal and the roof girts provide an air gap needed for insulating. Get some Kraft faced 24" (or what ever the span is) fiber glass insulation and tack it onto the rafters with the paper facing out, or some may use 1" R-max insulation board that comes in 4x8 sheets.
My first question to prospective customers when we are building a garage and they ask for insulation would be...."How to you plan on heating/cooling the space" ?
Here are a few photos from early in the process. Also attached is the color rendering we have created to approve the design with our customer.
More to follow.
Seems to me that a beam floating in space doesn't really equal a completed design project, however.... The engineer's assumption was probably that it was bearing on a concrete wall, that's what they would typically see, or jacks.
The best value in price should be seen if you keep the room width equal to 1/2 the span distance. Make sure the top chord size is adequate for your insulation needs.