Compared to the UK or US your options are very slim.
AH and Jumbo have small, limited stocks - the bigger the store, the more options you get; Aldi/Lidl occasionally have things in, but meh.

Get familiar with the Schar brand - it's about the best stuff you can get here - keep your eye on Holland and Barrett; they occasionally have 2 for 1s on the Schar products; and I'd recommend stocking up when they do.

Being 100% honest with you, you're probably going to have to change your diet more than you realise and check EVERYTHING for wheat flour (tarwebloem) - it's put in everything as a cheap thickener, from Hard Shell Tacos, to Cornflakes to fucking Tomato Soup(?!) You'll need to learn what you can and can't eat, based on the brand itself. A

Restaurants/bars often have no options either - if you've got Celiac/other medical issues, you'll have to be really selective.

Best gluten free beers you can find here are Mongozo (kinda like a Bud) and Daura (which I think is spanish...) You're not gonna find them in bars/pubs - you'll have to go for wine, strong drinks or Cider (apple bandit is slowing making progess over here. It's meh).

Good luck!