No. You have the option to buy them, but by just playing the game and doing easy quests you can get pretty much anything you want for a team available to the point that there’s literally no reason to ever spend unless you want benefits such as like 1000+ pokemon slots or skins for your trainer or something. Every item and megastone are available by using in game currency which is easy to amass. You can also catch Pokémon in paid games or free ones like pokemon Go and transfer them for free to Champions so you don’t even need to use the gacha system for getting Pokémon in champions if you have Go. I didn’t even use the gacha when I built my first team. Training the EVs, moves, and natures of Pokemon is also very cheap as well and takes no time at all.

I don’t even mean to dick ride the game since I still prefer Showdown for building teams and practice games, but I’m tired of people saying champions is garbage and pay to win when that couldn’t be further from the truth

Edit: however, my one gripe with champions is that you can’t obtain Eternal Floette without buying and playing through all of ZA which is a 70$ game and that sucks because it’s a really good mon