I'm not an expert, so I can only say what works for me. I have 150 grams of carbs per day - 40-10-40-10-40-10, the last 10 grams are optional.
It seemed frightening and insufficient at first, then it felt too much (260 grams of potatoes for lunch, for example), now I learned to combine different carbs. Today, for example, I had a lunch of a grilled trout, 130 grams of potatoes and 200 ml of fresh orange juice, and a lot of leafy veggies. Tasty and filling.
I also found very helpful to learn what a 'carb unit' is - in Slovakia, it's 10 grams of carbs. The doctor gave me 'exchange sheet' where I can look up how much I can eat: 1 unit is 20 grams of bread, 65 grams of potatoes, 45 grams of (boiled) pasta, 45 grams of rice, 70 grams of apple, 50 grams of banana...
And it's easy to calculate. For example, you want to buy some snack. It weighs 25 grams and the a label says 100 grams contain 55 grams of carbs. 10 grams have 5.5 grams of carbs, 25 have 13.75 (=1.4 units). So if your diet allows only 1 unit for a snack, you can't eat all of it - you can only eat 16.7 grams of it (2/3).
It looks confusing at first, but after 3 months, I see units everywhere.
My Mum was baking Christmas pastry, and it was easy to calculate that the whole dough had 88 units; but she made 220 pieces of it. So one piece has 0.4 units - I can have 2 pieces for a snack without risking that my BG will increase. (Which was quite liberating discovery... Christmas will be extra hard, the traditional meals are not exactly low-carb.)
This way I always know how much carbs I eat, and my BG is under control - my average before meal for last 30 days is 5.8, after meal 6.3 - so quite good, compared to 16 before meal and 24 after meal in September when I was diagnosed.
I've found I can have the odd slice of bread or oats without spiking as long as I balance the meal out with some fat / protein (i.e. 2 slices of toast is a massive spike but a sandwich is OK)
I found the same thing, and asked my doctor about it. She explained that fat slows down the absorbtion of carbs in your blood. Without fat, the carbs from bread are absorbed faster - so the peak is higher, but it also drops back sooner. Fat will cause smaller increase, but for a longer period. Both have advantages and disadvantages - if you eat bread with fat, and after 3-4 hours you have a snack, your BG will start at a slightly higher level than if you ate just bread.