I’m with MrsToast. If she expects a present already she is a grabbing harpy so you should save the money and buy yourself some running shoes.
However, if she has not indicated the requirement for gratification in the form of gifts, then she might be a nice person.
Tricky area because yes, you will be judged. Thoughtfulness and knowing what she likes (which will mean you have listened to at least two words rather than staring at her chest) will score big points.
Spending loads of money is out, as if she is a nice person she will think “what kind of slapper does he think I am that he can buy my affections”. If she likes expensive present, well then it’s back to the start.
If you don’t know what she likes you are in trouble, however help is at hand. Champagne. Not too expensive, £20-30 should buy you a bottle actually made in France.
If she doesn’t drink, you are screwed. Or not, as is more likely.
No need to thank me.