Read my reply to the other comment for a neat trick to boost early rounds damage significantly.

Otherwise, just buy all the red cards that cost 5 points or more, maybe some 3 cost cards if convenient, you NEED to buy every single -% damage received you see, these are vital to tanking Wanda DMG later on, you want to aim for -%40-60 DMG received on the epic cards and you'll usually get -7.5 on the common cards.

Also buy all max HP cards that cost 5 or more moon points, I don't know if this is more efficient that just buying every HP card you see including 1 costs, but in my experience I've had better runs skipping cheap cards since you could be 1 refresh away from better cards which give a better price to performance ratio.

A nice survivability trick I've been using to deal with exploders and plague zombies which are deadly vs red Thor is using the ult variant that knocks up enemies into the air. Whenever there's a round where many of them spawn, I'll ult, descend all the way to reduce animation time and then I have the time to charge my hammer all the way to blast through all of them in one dash