I don't want to sound nasty to the ever-patient, courteous, hard-working cabin crew - but they are doing a job and they are paid for it. On your flight there will be many cabin crew - so how many gifts are you thinking of giving? In my experience - be pleasant and courteous in return is sufficient.
Being nervous - I think everyone goes through it at some time or other - I did for a while and I've been flying now for years - at one point 60 - 80 flights a year. Just try to chill - learn up on a couple of relaxation exercises and if you have an issue ask/tell the caring cabin crew.