As long as you follow the path (See big image in my guide https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=626835851) you can start with whatever campaign you like and still get gold in 35 missions. However, if you do any missions that aren't on the path you may be considerably slower. In the end it does not matter that much: Everyone has plenty of time to get the golden coin.

Well done so far ^^
Ive started with wildfire missions first, i guess its the same thing, right?