Hard to know as it depends partly on what she's like as a person.
But things like, anticipating what needs done in the home without having to be told are a good start. So, making sure you're doing your share with the house and family for example, without her having to remind you or prompt you all the time. You see the kitchen needs cleaned, clean it.
I don't want to have to parent a partner and I'm sure they don't want to parent me either.
Then there's things like emotional support. Ask her how her has been. Maybe from time to time, ask her how she's feeling about life in general, if there's anything she needs to make it happier. Maybe sit down and have a discussion about how you both see the plan for the future. If there are dreams she would like to chase. And listen. And tell her you have her back. Anticipate and also, ask how you can support her in that.
Even things like anticipating 'oh, we are low on milk so we will need some later so I'll get some on the way home from work'.
I don't know how she with physical affection but hugs and random cheek kisses are usually good (unless she has young kids in which case she might feel touched out and need more personal space).
Complment things you like about her. Not false compliments but just when they are genuine. Maybe a little cheesy too. Like you think her hair looks so pretty when the sun hits it. And that when she laughs it's so adorable you still get butterflies. Sweet things. That show you adore her but that aren't sexual.
Then (and these are not a substitute for the above as you need to make sure you are doing your share, anticipating, listening, caring and being romantic) you could maybe buy her things she likes. Treat her to her fave takeaway or something (before she's cooked obviously), it doesn't need to be expensive. But her fave perfume never goes wring either! I'd do this AFTER you've started to put more work into the above stuff though as you don't want her to think that buying her shut-up gifts is what 'supporting' means to you.
Finally, she needs time both with it just you and her (date nights, no kids) AND with it just her. Eg, think about it, how much time dies she get to just herself? Does she have a hobby she goes to or a afternoon each week that she goes out with the girls? Often men have football or golf or go to the pub in the evening and women, get stuck in with the kid work. Consider if you're out too much. And, if she's not getting out enough.