Try not to start first because this deck is a counter-offensive deck, meaning whatever they push with, counter it and push with the units you counter with while adding more.
If you need to start first, I recommend either putting down the spear goblins or the witch first.
If at any time during the battle, they push with a Giant, I suggest countering it with Barbarians because they have quite a bit of health and they do a lot of damage.
If they push with a Balloon, I suggest countering it with Minion Horde because they will take the Balloon down before it does too much damage to your tower.
If you want to push, I usually use the Balloon accompanied by a Baby Dragon. If you don't want to use the Baby Dragon, I suggest keeping Arrows prime because your opponent will almost always counter your Ballon with cheap troops that can be killed with Arrows.
Another good pair I like to push with is the Witch and the Baby Dragon. I usually accompany these troops with Spear Goblins to do extra damage on the tower. This push is very costly at 9 elixir without the spear goblins and 11 elixir with the spear goblins, so I suggest pushing with this group after the one minute mark so you produce elixir quicker in case they counter the push.
I use the Mirror usually for double Spear Goblins or double Arrows. This is usually for when your opponent pushes on both sides and you need a cheap counter to it.