I usually ear less than 30gms carbs a day but sometimes I go up to 50.
My rule of thumb is nothing over 10gms carbs per 10gms, and most things less than 5gms.
So yesterday I had bacon and scrambled eggs for breakfast, grilled halloumi with lettuce and cucumber salad for lunch, and a grilled chicken thigh with salad leaves and roasted tomatoes and courgettes for dinner. I also had a piece of cheese as a snack. The tomatoes would have bumped up the carbs but I still came in at under 30gms. My readings pre and post dinner were 6.1 and 7.2.
I downloaded a really good app called "carbs and cals" to my phone and when I first started low carbing I used it to work out the approximate carb values of all my meals. I don't use it as much now as I tend to know roughly what I can and can't eat but it was really useful at first. I also kept a notebook where I wrote down everything i ate along with my readings so I could see what was affecting me. What I've learned is that I can't have any carbs at all in the morning, my body can't cope. But I can tolerate more in the evening. So blueberries and natural yoghurt will spike me hugely if I have them for breakfast. If I have them for pudding after an evening meal it's no problem.
Just keep testing after everything you eat and hopefully you'll work out what your body will tolerate and those numbers will star to come down.
Good luck