I discovered an interesting feature: When you have the Mind Gem on the Captain Marvel ramp, if you hit the button to spot the shot that will start the Binary hurryup... it also COLLECTS the hurryup in the same button press! So you just need to make the easy Widow shot to get the ramp multiplier.
So I used that with some new gem strategy to put up a 4.8 billion GC. Basically get Captain Marvel up and then collect big Soul Gem Jackpots there.
Do Mind Gem first of course, ideally without using any portal locks on it, since we don't care about the scoring from the Mind Gem quest itself. Stacking it with Thor is a good idea, since spinning the disc for Mind Gem also qualifies Thor's add-a-ball. When finished, put Mind Gem on Captain Marvel (this may be the toughest part, it's a bitch to get control and hit that without hitting any drop target or spinner or pop bumper!)
Bring Captain Marvel to 2 ramp shots (remember that the gem placement shot itself will count as one), then hit the button, which will both count as the 3rd shot and collect the CM side of the Binary hurryup, so you just need to shoot Widow for the multiplier. You can even do this with a caught ball so you're totally ready to shoot Widow. Bring CM to 5 shots and do it again. Easy 3x, and you can leave the Mind Gem there until you get up to 14 ramp shots to do it one more time for 4x.
Don't start any other gem quest until after Soul Gem, so that its jackpots will be available for all the following quests. And you can take advantage of Soul Gem itself to get some extra CM ramp shots in. If I get it down to the last shot with lots of flips remaining (can often do this with 40+), I'll take advantage of the time to pound CM a few extra times before ending the mode, I'm pretty confident in hitting the tower within about 20 flips if necessary.
After Soul Gem (and the third use of the mind gem at 15 ramp hits for Binary to 4x), then do Change Gems. Put the Soul Gem on CM, and Mind wherever you want, generally Widow is best since she's the easiest to level up. Now start gem questing for real - get portal locks for triple scoring, and ideally stack with Iron Man MB for some nice long victory laps. Now I pick quests based on the status of the Mind Gem at the time: when it's low level, go for Power Gem; when it's at level 1, go for Time Gem (use Mind for all three drop target hits); when it's level 2, go for Reality Gem and super-boom it all at once.
And of course for each of them, hit Captain Marvel for the jackpot of 200% or 250% of the quest score (if/when you can get it up to 5x with one more Binary.) I got four Soul Gem Jackpots each over 200M in that GC game, and up to 400M in another game (actually came from the Space Gem quest, thanks to Panther happening to be at level 2 via the Power Gem, and some lengthy victory laps.)
For Thanos Attacks, select whichever was your third gem (not Soul or Mind), and catch the ball to time it out -- so you can quest for that gem again and get another Soul Gem Jackpot! Go for the repeated gem quest when you have two portal locks, so you're most likely to win it and avoid losing the Soul Gem.
Once you finish all the gem quests, then change gems again for Reality to be on Captain Marvel, since that gives the biggest scoring in the wizard modes (Battle Royale, Super Victory Laps, and Trophy Mania.)
Short version: Exploit Captain Marvel's multiplier for big scores (sorry Pro owners!) Start with the Mind Gem on her for super-easy Binary hurryups, then Soul Gem for big jackpots, then finally Reality Gem for the wizard mode payoffs.