I work in the modern trade and lower retail trade industry.. with about RM150k.. in my opinion, you could open a very comprehensive convenient mart with you own branding.. On the 80/20 rule, I can say it is true.. 20% of your products would bring in the bulk of your income.. the remaining ones are to complement your core selling products..

In general, many business strategies could be used in a grocery shop/convenient mart to build up repeated customers; depending on the person's experience and business acumen..

Grocery business is about serving the needs of the local community.
Observe the residents profile in the area and we could strategize products pricing accordingly.
Eg. perhaps in a new township, you notice majority of the residents are married couple with a young child or baby. As a business owner, we could periodically hold promotions for baby products like diapers, milk powder.. etc to draw the customers. While they are there, we hope they would buy other things as well.

A real life example would be me.. I do my grocery shoppings at Sri Petaling. There are many supermarkets I can go but I always tend to go to Carrefour simply because I like Pokka Green Tea 1L and they sell the cheapest at $1.90 (normal price) compared to $2.80 at other places.

I do know certain marts selling a loaf of bread at RM2.00 instead of the official price to attract daily customers. Whether or not the strategy is working; they would know.

But then again, a franchised concept like 7-Eleven could have its pricing controlled.
Hence, flexibility in running the business is limited.