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When it comes to dietry advice, as a T1 of 18 years, my advice is as follows. Get into a routine. At first, test test test. Start to build a picture of how different food types affect your sugar level. The only way to do it is with experimentation; there are too many variables, but books like this can help (I have an old version of this).
Then, when your routine is established, if you can predict more-or-less what your sugar level is going to be (repeatedly and accurately), you can test a bit less frequently. I still do it 2 to 3 times a day just to make sure I'm on track. Every now and then it's too high or low and I have no idea why, but that's not really common these days.
Incidentally, while I'm writing this, I want to plug this app for recording levels/meals/injections written by Gordon Wong. It's vastly under-appreciated and thoroughly excellent. I have years of data in it, it supports exportable CSVs and under the hood it uses a SQLite database so it's easy to export/interrogate should you be that way inclined.
I use BG Monitor on Android
https://play.google.com/store/apps/details?id=com.wonggordon.bgmonitor