Gibberling is not drawn on first go now. The starting cards are relatively random in that you can get a mixture of a certain few. The card 'Arbor Up' is key to winning this battle. You need it in the first few turns ideally.
its very random fighting ragnaros in this solo mode , so there is no copy/paste for decks or for plays. 1-in general try to draw cards as much as you can. 2-fill the board with little minions, buff them when you can twice or more. 3-make the most of spell dmg / malfurion heropower. 4- avoid his aoe at turn 7 with little bait 5- *RNG is your best friend* you may need trying for a good 10 rounds
You need Will of the Wisps on turn 1, since it is a nature spell it costs 0. Then Ragnaros' 8 damage needs to hit Cenarius at least once to buff everyone. Second turn play call of the panther. Then face, all face, everyone, all the time.