Drop 4 money badgers(?) in the first column of the bottom rows. Next drop 2 slimes in the rows where the first two fire balls appear (1 infront of the other columns 2&3 . Then you literally just build from there leaving that first row empty until you're overwhelmed with income to just fill up the whole map (prob drop a 5th badger down too, not sure it matters tho).
With these types of games, you're meant to take some intentional hits (usually)