Since you spend RM2K and above, you need more than one card.

First card to get is OCBC Titanium MasterCard - you earn 5% cash back everyday for Petrol, Groceries, Telco Bills, TNB, Astro & Dining but the cash back is capped at RM50/month. So it is good for up to RM1K spending only. OCBC Bank will absorb the GST if you spend RM10K per year.

Second Card to get is Maybank 2 Cards - the MBB 2 AMEX earns you 5X Treats Points everyday PLUS additional 5% Cash back on Saturdays and Sundays. Once again, the 5% cash back is capped at RM50/month i.e. you only earn cash back for up to RM1K spending. However the 5X Treats Points is unlimited and works out to be approximately 2.5% returns which is better than any other credit card for generally transactions.

In actual fact, for your requirement the Maybankard 2 AMEX is better than OCBC - because you only need to spend RM2K and earn 10,000 Treats Points to offset RM50 GST compared to OCBC RM10K and yet earn 5% cash back on the RM2K spending.

And since you do spend above RM2K, maybe you even need another card purely for Petrol and you may consider UOB One Card or Citibank Platinum Cash Back where both cards earns you 5% cash back up to RM600 Petrol. Click here to my Credit Card Cash Back Page where I did a Comparison Table.