No no, i buy some cards that's true. But, the most of them are Rented, check some posts at splintertalks.io They have reallly nice strategies to rent. Because this new rental system you can rush to diamond or champion in less than 3 days, not this case, but it's possible.
It is difficult for me to invest, I go little by little for that, I always participate in the art contest to get more cards
Read some strategies, with the 1 day rental you can profit from 0 and start a snowball. You will just need to take time to rent every day... See this: https://www.splintertalk.io/hive-13323/@jacekw/testing-splinterlands-new-rental-system-peakmonsters-interface-2-from-1900-to-champion-league-with-668-dec-spent-on-rentals-