There's never not ways to earn Cookies, like how the above reply mentions that all levels above 100 grant 3k Cookies each time (it'll take a while to get there though, and it's also likely this game will get seasonal updates with new level progression). The Cookies you gain also increase about halfway into the levels, from 1.5k to 2.5k, which helps for sure (the final few even give you 5k). Weekly challenges exist too of course, and you're right, most people don't have much because the game literally just launched.
My question is... Have you been trying to save up, or have you already been spending a lot on the common/recurring skins? I've been playing since Playtest 3 so I had a head-start, but between getting to around level 33, achievement-hunting, doing every single weekly challenge, I was able to afford both Ori and Naru, as WELL as the F.I.S.T. Rabbit when it was in the playtest shop, for what amounts to like, 48k Cookies. Padded out with 1-time achievements, sure, but the game literally just launched and I've had no issue earning them with engaged play so far. As the game gets further and further into its lifespan, I can imagine dedicated players sitting on mountains of the stuff. That even said, don't worry yourself trying to buy literally everything, pick out your favorites and focus them. Most of this stuff will be back in shop rotation several more times too, though I agree, these are a lot of pretty expensive things to throw out so soon after launch, at the same time.
All else fails, as an emergency dip, you can always convert some free-earned Nemo Bucks into Cookies...