A1. It depends on the armor you're applying it to. Also, with the new dye system I think some of the old combos won't mix the same and I haven't seen any new dye charts made.
A2. Order doesn't matter.
I did gold on one of my chars the other day and silver+yellow+yellow looked the 'most gold' on that armour but as others have said, it depends a lot on the armour your trying to dye.
As most have said, Gold could be made with Yellow and silver (possibly brown, also)
But if you're on a tight budget, you can always try yellow and grey (though not too sure of the outcome)
The old classic mix was yellow+silver+orange+silver.
Looked pretty good on the monk but it wasn't a shiny gold. On my warrior it turned everything a coppery color that's interesting but not what I would call gold.