Welcome!
First of all, good for you for thinking about this. Really thoughtful of you!
I'm 17 weeks pregnant with our first as well, and I would say the nicest/most appreciated things my DH (thats Dear Husband incase you're not au fait with the Mumsnet acronyms!) has done so far have been the little daily things like asking how I am feeling, bringing my cups of tea or glass of water or snacks etc, making sure he is around to carry things like shopping etc. He stocked up the house with ginger biscuits and Sprite when I was struggling with nausea.
When we first got our BFP result, he bought me some flowers and a lavender scented pillow spray. Just a nice treat :)
If you have a cat or anything, make sure you take over things like changing the litter, cleaning up after it. This is more a necessity than a nice gesture, but something you should start right away to keep baby safe.
He read up on the NHS guidelines on what food I shouldn't be having and makes sure our shopping lists/meals together dont include this so I dont feel like I'm missing out.
I have also really appreciated his interest in how the baby is developing, it means a lot to me that he wants to be involved and clued up as to what fruit it's the same size as each week etc.
He's come to my scans and midwife appts with me and always asks really good questions, things that wouldn't occur to me.
He often tells me thank you and says I'm doing a really good job of growing our little baby, which means a lot to me.
It's just little things like that that really mean a lot, and make this whole journey really exciting and enjoyable when the woman can feel really quite rubbish - with the tiredness, nausea and hormones, especially in the first 12 weeks.
He also bought me some non-alcholic white wine to take to a party we were going to, which was really sweet of him. Turns out the "wine" was rank but still a really nice gesture.
My advice is just be attentive and ask how she's feeling. I'm sure you'll be great, you sound like a really thoughtful partner.