To start off the game you should start a card in the back.
Preferably Dark Prince in the back or Electro Wizard.
This period of time is just learning their deck and keeping their win conditions and hard counters in hand.
If you know the current meta you should have a good guess as to what deck they’re playing by the first 3-4 cards.
For example if someone plays Mega Minion, Night Witch, then Baby Dragon, I immediately know that this is almost for sure a Golem deck.
Another one is if they play a Goblin Gang, then a Pump, then a Miner/Minion Horde, I think it is 3 Musketeers and I change the way I play.
You play different against 3 Musks vs against Golem.
Cycling chip damage at the beginning is never a bad move.
Use Ice-Spirits, E-Wiz, Dark Prince, and Zap. P.E.K.K.A and Magic Archer as well as Tornado and Poison should only played reactively, E-Wiz is not so much but I like to save him so I don’t get punished with Inferno Dragon or Sparky other lane.
Their Tower should be down to 2000-1500 by now. You should be playing reactively.
Then after you defend, go for a huge counter push.
Try to play smartly and switch it up.
Do something that your opponent would never suspect, like a P.E.K.K.A on the bridge other lane.
Doing something bold will almost always pay off in the end unless you do it to much.
Also during Double Elixir is the time to do predictive plays and lots of them.
If your opponent is playing bait you can drop the Dark Prince behind the king Tower a little bit before your opponent Goblin Barrels and the Dark Prince will completely splash all of the Goblins if it is charging.
Or if you know your opponent will Golem in the back, pressure other lane when you think they are at 10 Elixir and will drop the Golem.
This deck chips very slowly so it is better in challenges since overtime is a juicy 3 minutes.
You should be playing a lot of Dark Princes at the bridge pressuring their opposite lane.
I would generally play P.E.K.K.A in the back same lane as their push.
Once they overcommit on their push to kill the P.E.K.K.A, I drop another other lane, then I just rush them as fast as I can.
I only do this against beatdown decks and if I think I won’t be able to beat their next push.
A lot of people don’t expect a P.E.K.K.A at the bridge and they won’t have enough to defend it.
Once your Tower is super low stall by Tornadoing everything back.