Specifically for people who came and gave cash gifts, and people who didn't come and sent money gifts. (Not large amounts but very nice gestures)
He got mostly seforim not money and those are easier to write...
I have, as samples to help my son:
Thank you so much for coming to my bar mitzvah.
I was so happy to see you and dance with you at my simcha.
Thank you for the meaningful card and the generous gift. ??? And I don't know what else...
If the gift was an item, I.e. a sefer or kiddush cup, can end off with, "I look forward to using/learning from" etc
Right! He mostly got seforim and that's how he's ending it. But the cash thank you sounds so abrupt. Does he say something like, "I hope to put it to good use"? Does that sound mercenary? Happens to be the cash gifts were really respectful gestures (not large amounts, nothing over $100) mostly from ppl who didn't come but have respect for my husband and his rabbinic role in the community, and I don't want the givers to feel like it was taken for granted.
No, I'd leave it as "generous gift" for cash. Maybe use "thoughtful card" instead of "meaningful" and then use the term meaningful for something like: "your participation at my simcha was meaningful for the whole family. May we share in future simchos"