Had the ISO already saved up to champion Kate, so did that as soon as I got the bonus. Then opened a bunch of legendaries, then championed Moon Knight, She-Hulk, and Squirrel Girl. The rest went into random levels for 5s, and restarting the cycle on some 2s.
Update: decided to champion Daken also.
I took Surfer from 300 to 450 (463k ISO!), and Black Suit Spidey from 358 to 420 (198k ISO). Then I champed Moonstone, 2* Wolvie and 2* Bullseye (recent flips from max champs).
All that left me with about 8000 ISO, down from 896k.
(Cue South Park “aaaaaaaand it’s gone” pic)
I champed She-Hulk, Doom, and Ragnarok, and leveled Squirrel Girl, Doc Ock, and Quicksilver to 153. I’ve got just enough leftover to champ them too, but they’re each shy one cover, so I’ve got to wait on that first.
And then I’ll be done with champing 3*s.
So the shorter version is “I finished champing the 3*s.”
(for the record, I’m rank 54, and have several usable 4*s, but only one fully covered, and none champed, so I’ll be moving into that territory next)
I champed 2* Torch, Marvel, Wolverine, Moonstone, and Cap. Never had the spare ISO to bring up most of my 2s and it was nice to finally make them somewhat usable for their essential nodes (and DDQ, when I can’t use Mags or Storm). I have 580k leftover - gonna save up to a million and then open my LT/CP hoard.
I championed some characters I had covers queued for: 3* Captain Marvel and She-Hulk (both took ~100K each), and 2* Wolverine (recently recycled for champion farming, still had 30K to go). After adding a few more levels to some other 2* recyclees, decided to bank the rest as I don’t have any covers queued anyway.
She-hulk
3* Marvel
2* Marvel
Gamora
XFWolvie
Now I have about 200k left and I can’t decide if I should max Thing or Ghost Rider, or level several 4*s to 200ish. Really wish a run of bad luck hadn’t screwed me out of that x23 cover in Nefarious Foes. I’d be able to max her.
Maxed and champed She-Hulk
Softcapped 4* Deadpool (at 209)
Next order of business is “4* maintenance”; bring some of them up to softcap levels, though only if they’d be 150 or more. If I have some ISO remaining after that, plough it into championing the rest of my 3*s (to avoid wasting rewards).
Was currently working on Carnage, Carnage 220>Champ. Next plan was Dino, Dino 220>Champ. Champed Moonstone/Bullseye, and have around enough to champ the rest of the 2*'s which was my next plan.
Basically it gave me a season and a half worth of ISO to drop at once, so it accelerated my plans to the next phase that was planned on after anniversary (continue hoarding CP, open when IM is in classics, have enough ISO to champ a 4* at that time and not waste to many covers).
ISO is needed, ISO is great! I’m still several million in the hole, however.
Also - no covers in this list yet, huh? I still see no method to 5* transition. Hopefully that’s phase 3.
daredevil, ock, falcon, doom. 2bullseye, axw, 2daken, 2cap, hawkeye, moonston, bagman. then, after 395 tokens, quake. and I’m ~67.25 now.
I champed Starlord, X23, quake, and Mr. Fantastic, as they all had covers in the queue.
Spent 155k to finish XForce since I had an expiring cover.
Sitting on the rest right now. I have a huge token hoard waiting (by my count I’m sitting on 1916XP worth), I’ll make decisions around the anniversary.
Champed 
from 210,rechamped 
and about have about 48k left.
Championed 3 3*:
Black Panther
GS Black Widow
She-Hulk
All 3 had at least 1 cover so I got 3 LTs as well.
Just doing that I got 95% of the way to the next rank.
Champed 3 4*:
Have 275k ISO left.
Opened some tokens for the xp and now have to decide between
for my next project.
Champed GSBW - got a IMHB black, so he’s up to 11 covers!
Did some 4* maintenance - leveled everyone that was under 15K to bring them up to their cover max.
Also champed my recyclables OBW, Thor, and CStorm, as I had 6-8 covers in queue for them.
Still sitting on 389K that i’ll keep until i need someone like 4Pool for DDQ or something.
(was a level 52 - 624K ISO)
I somehow got 867k from being Rank 65
Champed Chulk, Ghost Rider, and Venom to clear out the covers in my queue. Legendaries pulled a Thing, so he’s next on the list, but I need an additional 100k ISO.
Much like a lottery winner, I plan on blowing my proceeds on worthless junk. Level 270 Cho? Duh, I’m ISO RIIIIICH!
Followed by a large dose of buyer's remorseSo far, I’ve Champion’d 
& 
since I was holding covers for them already. I’m holding onto the rest to see how I need to apply it over the next couple of days.
I was at about 700K after the influx. I spent it on maxing out 7 2-stars. So, now I have everyone championed from the 2 and 3 star groups except Ares. All of the covers I get from my tokens will be champion levels or get more closer to maxing a 4-star. I’m really close on several. And, I still have about 200K left! This was a very welcome ISO boost today. 
I haven’t, yet. I am considering bringing Drax and Peggy Carter up to their softcaps, and maybe champing Mr Fantastic. I should still have a million after that, which is what I need to max out OML and Phoenix…