Hey, I was diagnosed at 20 weeks and started on insulin throughout the day slow acting (2, 2, 2, 2) (morning, lunch, evening, bedtime)
I'm 38 weeks tomorrow and I'm on slow acting insulin (2,4,2,4) and fast acting (6,4,2,0)
It hasn't increased as much as I thought it would have, honestly. But, it will depend on a lot of factors including factors over which you have no control. Mine has been well controlled and I thought that was because I was on insulin, but my midwife told me that some women simply cannot control it, and get crazy highs and lows even with adjusting insulin along the way. It's hormones. It's nothing to do with anything else.
As far as induction is concerned, the evidence doesn't stack up for induction if the GD is well controlled, uncomplicated, and there are no signs of an abnormally large baby or placenta problems. That said, it's still policy in a lot of places. Seems to be 38/39 weeks depending where you are and on your own feelings on induction. Some women choose to refuse induction and request careful monitoring instead.
You will probably receive extra monitoring as a result of the GD as well.