You can earn Tier Credits by making purchases on Caesars properties provided a Total Rewards card, 1 TC per dollar spent.
I do not know if the Tier Credits daily bonuses apply to only tier credits for gambling action only. If it is not limited to that you spend $5000 on a single day, weather it be buying 100 buffet passes at the Bacahnal or multiple luxury hotel room stays.
Otherwise spending $15000 in a calendar year will get you Diamond.