Of course it all depends if your own stuff is any good!

Folk club audiences are normally very tolerant. But they have been subjected to lots of self indulgent 'singer-songwriters' over the years and might be quite wary. If you are doing a floor spot, try a traditional (or better-known) song first and then ask the audience if you can do one of your own songs (of course they'll say yes, they're a folk club audience). And then give them your best shot. You should get a reaction from this that should tell you whether your next song should be one of your own or not (if it's a three song spot). Also choose your clubs well. If a club is known only for its traditional outlook they may be against you to start with!

At the break or the end ask for criticism from the organiser or members of the audience.

Good luck!
Les