Hi and welcome.
So sorry to hear about your diagnosis but good to hear that you have a supportive nurse.
Yes 94 is a lot higher than you want it to be and your readings of 15 and 21 are in the ballpark to correspond with that HbA1c of 94 so not surprising.
Things you need to know....
Metformin takes weeks to build up in your system to have any effect and the dose is slowly built up week by week to the full 4 tablets a day to allow your digestive system to get used to it, so 1 tablet will do absolutely nothing!
Gliclazide encourages your pancreas to produce more insulin so that will be a bit more effective, IF your pancreas is able to produce more insulin.
What will have a much bigger impact is what you put in your mouth..... and it is not all about sugar as many people believe. All carbohydrates break down into glucose in the digestive system and get absorbed into the blood stream and there are carbs in almost all foods to a greater or lesser extent. Reducing your intake of the foods which are high in carbs and eating more of the lower carb foods will have a significant impact on your BG levels and in fact your test this morning shows that because your BG levels jumped 6mmols as a result of eating granola with milk? Depending on the brand and variety, granola is about 60-65% carbohydrate. I am guessing that you didn't weigh your portion this morning but if you go back and tip a similar amount into the bowl you used and then weigh it, you will be able to calculate roughly how many carbs were in it. Add to that the carbs in the milk (lactose) which is the natural sugar in milk and you have glucose going into your blood stream from the granola and milk to push your levels up.
Obviously you want to cut down on the cakes and biscuits and sweets and added sugar in your diet but the other carb rich foods also need to be reduced in portion size. Theses are anything made with grains and grain products (flour etc) so bread, pasta, rice, breakfast cereals, couscous as well as starch veg like potatoes (including sweet potatoes) and parsnips and fruit is also high in carbs because they contain natural sugars (fructose) so reducing the amount of fruit you eat and limiting it mostly to lower carb options like a few berries which are nutrient dense and pack a lot of flavour for a small portion is a good choice and limiting the tropical fruits like banana and mango and pineapple and oranges (and grapes) to a very occasional treat.
I would stress that it is about reducing portion size and frequency of these foods rather than avoiding them although some of us do choose to avoid them. The key is to find a balance that you can maintain.
It is also very important to point out that if the Gliclazide does work, it needs some carbs to work on so drastically changing your diet overnight might cause you to hypo (your BG levels to drop below 4 and be potentially dangerous) so making small sustainable changes to your diet is vital. Also, because your HbA1c is pretty high you don't want to drop it too quickly as that puts pressure on the fine blood vessels in the eyes particularly which are very delicate. You may experience blurry vision anyway as your levels gradually come down and this will usually last a few months but coming down too fast can put you at risk of more permanent damage so do go steady with changes.
Having listed a massive range of foods which will likely cause you BG upheaval, I think it is only fair to mention the ones that almost certainly will not and some of them may surprise you.... Meat and fish and eggs and mushrooms and cheese and most nuts (beware peanuts and cashews as they are slightly higher carb) are pretty low/negligible carb. Veggies which grow at ground level are usually good, particularly leafy green veg like cabbage and kale, spinach and leeks (usually cooked with a knob of real butter or cream cheese) and salad leaves (usually served with a good dollop of full fat coleslaw) and cauliflower is an amazingly versatile vegetable and great for us diabetics.... can be mashed to replace potato with a good dollop of full fat cream cheese and a liberal sprinkle of hard cheese if you fancy. It can also be grated or chopped and used to replace rice of bought pre prepared as well as served as good old cauliflower cheese but instead of making a sauce with flour and milk, you just par boil it and then coat in full fat cream cheese and grated cheese and brown off in the oven. Dairy produce.... full fat is generally lower carb than low fat, so a better choice. Many of us have real double cream in our morning coffee instead of milk because it is lower carb and tastes luxurious! Berries as mentioned above are the lowest carb fruits, so many of us have a portion of those with some full fat Greek style natural yoghurt, mixed seeds and/or chopped nuts for breakfast instead of cereals or toast. There are lower carb granolas available but still about 50% carbs so if you want some we find it better to just have a sprinkle on our yoghurt rather than a bowl of granola with milk.
You will notice I am sure that higher fat products rather than low fat, feature quite a lot and there is a good reason for this, despite the NHS low fat advice. Fat is slow to digest so it keeps you feeling full for longer and provides much slower release energy that carbs. fat also slows the digestion of the carbs you eat with it, so having that very occasional banana with some full fat natural yoghurt or cream should mean it has less of a dramatic impact on BG levels. Only a very small percentage of fat can be broken down into glucose whereas about 40% or protein breaks down and pretty much 100% of carbohydrates. Carbs also break down very quickly to give you a spike in BG levels between 1-2 hours usually. After that, your BG levels start to drop and your body feels that drop and tells your brain that you are hungry because your BG levels are dropping rapidly, so you want a snack 2-3 hours after you just ate a meal. Once you cut the carbs and eat more fat, you don't get those spikes and drops and you stop getting the hunger pangs and you actually need less food as a result. I often just have one or two meals a day and don't feel hungry in between whereas before, I was ravenous all the time and looking for what I could eat next.... I love how easy it is to just eat what my body needs now instead of constantly craving and eating. I have control and I don't even need willpower!
Anyway, I have typed far more than I should have and really must stop because I have almost certainly overloaded you with info and we all know how overwhelming that diabetes diagnosis is in the early days and weeks.....So apologies for that but do come back to it and reread as you will no doubt take more in.
Any questions, just ask. That is what the forum is here for.