How you modify cards is important. High blood costs are hard to play and need to be worth it. It’s been a while since I played but I found most success with keeping blood costs down, cards that return to hand when destroyed, and attacking multiple lanes. Stinky is also surprisingly useful at times.

My first successful run was as a result of creating a card that cost 0 and returned to my hand when killed. You definitely need to play a couple runs to build up a strategy and create some cards that go in the deck.