First, welcome. You have come to the right place and you are among the most fantastic and knowledgeable friends. I was diagnosed as pre-diabetic a few weeks ago and I cannot speak highly enough of the members of this site.
@everydayupsanddowns, in particular, is a mine of valuable advice and I see that he has already weighed in.
The following thoughts are very personal to me and my sort-it-immediately personality.
A wise man once said "If you don't measure it, you can't manage it". At the very least you need to be doing the Fingerprick tests. Once you have got the hang of those, you can get one Constant Glucose Monitor for free here:
https://www.freestyle.abbott/uk-en/getting-started/sampling.html. This will give you all the data you need to see what food causes what Blood Glucose reaction.
It will even provide you with a very detailed report including average BG and estimated HbA1c. But you only get one free, it lasts for 15 days (in theory, mine started to die after 10) and they are £50 a pop after that. So the key question is when you use it. And this depends partly on how you plan to attack your diagnosis. I threw everything I had at it. My BMI was 21.6 and I already exercised a lot so it had to be diet.
Within 24 hours, I had yanked out all the carb I could with the exception of porridge. Breakfast cereal, golden syrup, toast, rice and pasta plus a mountain of energy bars were replaced by fruit, yogurt, cauliflower rice plus trail mix. Three days later, my 2-hour after food FP test was below pre-diabetic levels. Six days later, my average BG was down to 5.2 and I had lost 2 kg without ever feeling hungry.
The monitor allowed me to see what food did what to my BG and gave me confidence that my HbA1c was heading back to where it needed to be. As something of a nerd, I really got into watching the BG ups and downs (sad I know) and diving into the detailed reports. It also gave me the confidence to add complex carbohydrate back into my diet because the weight loss was becoming a concern.
I am not for a minute suggesting that your path to where you want to be will be as simple as mine or even possible. I was just pre-diabetic, you have been diagnosed as diabetic (as
@Docb says, it would be handy to know what your HbA1c is to see how much work you have to do). But you have weapons I didn't if you could comfortably lose weight and do more exercise.
All the best.