Buying summoners? Upgrading cards? No need for any of that. A fresh account currently requires no more than 2 cents a day to rise to silver, earning an average of ~$0.30 daily which you can trade for crypto, potions or better cards.

Considering a new account costs $10 by itself, that means you get that money back within the first month no matter what! Where do you go from there? That's up to you.

How to get to Silver for 2 cents a day

Choose your favorite splinter and a super strong legendary card to go along with it. Rent that card. Now you have a card to carry you to silver even using just a level 1 summoner. Profit.

Fire

Hydra

Water

Ruler of the Seas

Earth

Minotaur Warlord

Life

Sacred Unicorn

Death

Corrupted Pegasus

Dragon

Dragon is not recommended because it doesn't allow you to complete daily quests.

Which splinter should I pick?

Choose whatever splinter has a daily quest up for you. Just remember you should still be able to make a decent team composition if you want to win.

Rental market dependency

This strategy relies on cheap enough cards for rent on peakmonsters. Search throughly. If there really is nothing, then wait until a good opportunity shows up. But there is usually something cheap you can grab.