Voucher hunting is an avenue you can look into if you wish to reduce your monthly expenses. I mainly target NTUC vouchers and try to get them at close to 5-10% discount to value. You can also consider CapitaMall or Capitaland vouchers which can be used for NTUC situated within Capitaland buildings. The reason I prefer NTUC vouchers is because you can practically buy anything from their hypermarts.
Citibank SMRT card gives you a 7% disc to NTUC groceries, but with a min spending of $600 per month. Using your Frank card with your Citibank SMRT card forces you to spend a min of $1,100 a month. A more ideal scenario will be to buy discounted NTUC vouchers online, as this will reduce your credit cards and total min spending, which will equate to more savings per month.