I don't believe there will be many 0 or 1 mana costs in chaos legion, especially within neutral splinter, unless there are some really interesting summoners. Dice already has a 1 mana cost unit for each

Sign me up for the giveaway, would love to grow my water collection

I would say your ROI drops as your go into Gold 2 or higher as you need to have better leveled cards in order to win. Best ROI imo would be to get a silver level splinter in gold to get the DEC bonus %