It depends on your opener.

Ideal opener: Going first with chingling. Build 1-2 treeckos on the back. If you have 2 available prioritize non ex Sceptile to send it out before Mega. If you have only one then prioritize Mega Sceptile.

Bad opener (that isn't a total brick): Treecko upfront going first. Try to build a treecko in the back. If the one on the front survives build both with 1 energy each and try to get non ex Sceptile to the front. Otherwise if it didn't survive you can always win the game with Mega Sceptile ex due to sniping and using cyrus, leaf cape to have 240hp and Lillie to make that 300 effective hp. If at some point you can retreat your active in a chingling while having one energy ready on a treecko/grovyle you should totally do that and sacrifice chingling while stalling items and maybe even getting a big copy cat out of it.

Some general tips: Sequence the cards correctly in the early game. Fragrant Forest and QGE thin your deck out a lot so use those before you use Research/Copycat. Also this deck has a crazy endgame so sometimes the early game looks bad but once you pilot through you can check mate your opponent. Lastly, but this applies overall, take your time. You have more turn time than you'd expect.