Most instructors don't expect a thing in return, unless it is common practice at your club to give some sort of gift. The look
in the pilots eyes when they do their first upright landing and
their first solo is reward enough. I've trained quite a few students
and it was just recently that one offered a steak dinner and
another is a HVAC expert, who came to my store and did an AC
checkup in trade. If you feel the need, then a dinner and drink
would be more than enough. But most important would be a
sincere thank you. In the next year, offer to train someone and
pass on the favor. This is what our hobby is all about.

Randy