As has been said, it is all trial and error, and you can start with one amount then change it, but always eat to your meter.
Personally I really could not envisage the rest of my life without bread or spuds. The rest didn't bother me. I devised a diet round the foods I like using portion control for the carb elements. I started with 126g a day. That didn't work so I reduced to 95g. I still wasn't happy, so ended up on 60 to 65g and am still on that amount. That is my safe amount. I can still eat a slice of bread (heavily seeded wholemeal) or have 2 or 3 small spuds (roasted, boiled or fried, not mashed or jackets) so I am happy and can sustain this without feeling deprived or tempted. I could not have done that without my meter and my jug scales. But that is me personally, and will not apply to everyone. I also stuck to 1200 calories whilst I was losing weight. This has now been increased but my carbs will stay the same.
Whichever and whatever, just make sure you can sustain it.