Hi Ardiana,
I started off with just bringing my cards & tags to shows, then branched out into other areas as I found more things to do with paper.
For cards, I bring everything I have. Birthdays, seasonal holidays, thank yous, everyday cards...I try to have a few of each print and type so that people will be able to find what they're looking for. At this point I pretty much make inventory year-round, but I really ramp up production about a month out from the show. Of course, I'm still up until the wee hours of the morning finishing SOMETHING the night before! LOL
The only items I currently offer custom are my wedding invitations. For those I bring my sample binder with me and send people off with my card to sit down another time. Let's face it, no one is going to buy wedding invitations at a craft show and I don't have the time to devote to them there.
Hope this helps!