the snow event really is just pure garbage its almost over and i still am not getting near enough resourced to actually progress beyond battle 23
One thing that I figured out a little to late is that resource producers don't scale linearly. Don't know how much exactly you get with each subsequent one, but it's definetly some sort of multiplier. Doesn't help that there's nowhere in the UI that shows your income. So I think the best strat would be to pick only water, upgrade loot rating a shitton of time, then reroll everything into crit producers, get a buch of crit rating and then reroll all producers again, this time into snow. All while picking every crit related combat item you can.
Too bad that this can only help in hindsight. I personally picked the producers evenly, which is probably the worst thing you can do.
The costs scale to basically unachievable levels after not that many upgrades though, I don't think it would be worth the snow rerolling producers multiple times. Maybe once to farm up loot rating at the start, which is basically mandatory to get very far, but after that a more balanced distribution will get you maybe 1-2 fewer upgrades in each thing without being a hassle and a big drain on snow. Then you have a lot more chances to repeat fights or reroll bad loot / fix your build. By the mid-20s or so producers become irrelevant, you just pump them all into 1 or 2 things so you can maybe afford one more upgrade before the event ends, but one loot reroll can take you from barely scratching an enemy wave to progressing easily again.