Each team comp has core cards. Cards that are absolutely irreplaceable cards, without which the comp falls apart. So you should study the meta by keeping an eye on the leaderboards, and watching replays. There are so many tools such as Axies.io and YouTube where you can watch gameplay of a certain comp to see what works and what doesn't.
Let's take a Feather comp as an example. Search for the Rune that every feather comp uses, Feather Descend, in Axies.io. You can see that there are two core cards: Feather Spear and Tri Feather.
For a Bubbles comp, we can check the Heart of Ocean rune. The cards that pop up into every single winning comp are Sponge and Nimo.
For Bleed, let's search Brutal Claw. Chubby. Arco and Gerbil are prevalent.