OKAY: Jaskier buying gifts for Geralt (I'm sensing this could go either way too..)
ACTUALLY, it's my personal headcanon that Jaskier is really, really good at gift-giving. He just. Fucking rocks at it. Because he's naturally so attentive and intuitive, finding the perfect gifts for people comes easily to him.
And then Geralt came along. GERALT, at least at first, is a conundrum to Jaskier because before they met, Geralt had never RECEIVED a real gift before. Gift-giving was a foreign concept to him. He also doesn't know when his birthday is, and didn't celebrate Christmas/Sovan/Midwinter like most people do. Anything he needed he just purchased for himself, and he didn't seem to WANT much of anything. All of this left Jaskier kind of floundering because HE IS A GIFT-GIVER. HE LOVES GIVING GIFTS. HE LOVES SHOWING HIS AFFECTION THIS WAY, but Geralt was making it exceedingly difficult.
Gradually, over time, Jaskier learned to dole out his love in smaller packages, paying attention to when Geralt was running low on supplies for his potions (for example), or noting when Roach's currycomb was looking a little worn, and just picking up little things for Geralt as gifts here-and-there throughout the year and their travels together-- though he does make a point of getting Geralt SOMETHING for Christmas/Sovan/Midwinter, even if it's just one of his favorite pastries.
On a side note, the only person Jaskier is shit at buying gifts for is Yennefer, and it's not his fault at all. It's because no matter how good the gift, no matter how perfect and spot-on it is, she always says she hates it. Flatly. To his face. (Then she keeps it and loves the ever-loving shit out of it secretly while Jaskier practically foams at the mouth out of frustration.)