Please don't beat yourself up about this, or put so much pressure on yourself to "get it right". NSD is definitely worth trying, and can sometimes give really good results, but there are no guarantees that it will be the total solution - no matter how rigid you are about diet. It just doesn't work for everyone, and even when it does work, there are people for whom a low starch diet (which is much easier) gives as much benefit as a strict NSD. You are only going find that out by trying. Most folk seem to see it as something they can do themselves in addition to conventional medical treatment, not instead of. If you want to try, you have a range of choices:
If you want to go really strict NSD, then you can't get away without buying a bottle of iodine and testing every single thing before you eat it. You may also need to consider what is in the pills or supplements you take (most have starchy fillers of some kind). It will be a very restrictive diet - theres no getting away from that.
If you want to just do your best with a "common sense" NSD, then you absolutely avoid all the obviously really bad stuff (grains, starchy veg), and compromise a bit on the kind of things that may have very low levels of starches in, as well as finding out whether that particular fruit or vegetable that might be starchy is better eaten raw or cooked (cooking changes starches in a lot of things).
If you want to make it easy on yourself you try low starch first (avoiding all the obvious things like grains and obviously starchy veges) and see if that makes any difference first - then when you get used to that you can decide whether to be more restrictive.
And, remember that if you do flare while on a low starch or NSD, then it may not be a diet slip-up that caused it - it may just have happened anyway.
Just do your best, and do what makes sense for you. You can't do any more than that.
