Another point I’d like to bring up is the lack of draw supporters. Since a deck like this needs to set up all of its Pokemon as early as possible, having 10 draw supporters (I don’t include Ghetsis because it hardly helps sets up and disrupts the opponent more than help yourself - I think you have put it into the deck just so you can score a large draw off of it when your opponents hand accumulates, which isn’t a bad reason but I think it would be unnecessary to draw lots and put dead cards back into the opponent’s deck when you should be in a comfortable position anyway).
So I think you should try out:
-1 Psychic Energy - attacking with Sigi/Trevenant isn’t what you should be attempting but I feel you may still want the option
-2 DCE - This will either help power up Donphan for wreck or it will be paired with Sigi/Trevenant
-1 Ghetsis - refer to the most text I have ever put between 2 brackets.
-1 Silver bangle - refer to B_M’s post
-1 Evosoda - it may seem counter intuitive however a supporter would fill the role better as it has the chance of getting a basic.
+1 Float Stone - retreating is a main part of your strategy, it’s too important
+2 Fighting Stadium - B_M
+1 Muscle Band - B_M
+2 Supporter (Skyla/Colress/Shauna)
Other things: Pokemon Fan Club, Froslass PLB, more supporters