I was diagnosed with GD at 28wks, prior to this my urine glucose had been pretty high anyway.
As well had testing my blood sugars 4x day, I just followed the dietary advice given to me by Diabetes MW. This was:
Swap white bread/ pasta/ rice for brown.
Beware anything 'Low Fat' as normally loaded with sugar. Especially yoghurts - I ate natural yoghurts flavoured with a bit of fruit.
Keep off the biscuits chocolate etc - that was really hard so when I was really craving a bit of chocolate used to eat a few chocolate buttons. BTW Wholemeal scones/ biscuits ok in moderation.
Beware dried fruit as this tends to be high in sugar as well - which put paid to sultanas on my Bran Flakes!
No sauces on food (boring!) but keeps the sugar content down. Try to avoid processed food, and if you need to make a sauce for e.g. pasta - do homemade ones - that way no hidden sugar.
I tended to eat small amounts very regularly (every 2-3 hours)- and load up on veg to try and fill myself up. Also tried to be as active as possible (walking, bit of housework) to bring the blood sugars down as well.
Following this meant I avoided having to go on Insulin, and to be honest felt really healthy and didn't have a huge weight gain which I did in first pg.
Baby weighed in at 8lb 13ozs