I actually just dived right in and got 4 splinters worth of cards and to over 100k power for gold 3 league. Have had some bad RNG but also eventually need to get a couple of legendaries to help out, but got a lot of gold cards for the increased DEC gain when I win more.
So I am covered for numerous splinter daily quests and the rental system is great, especially if a newcomer can even just get to having 100 - 200 DEC as their startup!