A HbA1C of 54 is not too bad. Mine was 99 when I was diagnosed and 59 three months later. I am hoping to get under 48 at my next test in May.
You just need to avoid sugar and carbs such as breakfast cereals, bread, potatoes, rice, pasta and avoid fruit juice. Fruit can have a lot of sugar, especially bananas although strawberries and blueberries are not too bad. You can eat more fat such as cheese, butter, full fat yoghurt, cream, avocados, nuts etc.
If you get a blood sugar meter you can see what your blood sugar levels are and which foods spike them. Ideally you want a level 4-7 before you eat and not more than 8.5 afterwards. I found that porridge make my sugar go up to 10 two hours after eating it, so I stopped eating it. Some people find that it does not effect them. If you want some chocolate then Lindt 90% Cocoa is low sugar.