-buying a booster
-tourneys (max you can make off tourneys is about 10k a day)
-bets (very unreliable, i wouldnt recommend it)
-duels (if youre good enough you can get rich in 1 day without needing tc to start)
-making art and selling it (very time consuming. also the market for art is bs, chances are you will make nothing)
-marketing (easy money, but you need to know the average prices for alot of items and which items are popular, also you need to have alot of tc to do this efficiently)
all in all, you need to be good at something to make quick tc(or you can buy tc, even if it is weird and lame).