If you are a covers band and go out as such I'd say max one original song per set. So that's two in a typical two-set pub gig.
And then only if they go down OK.
Perhaps consider running an originals set on the side under a different name. For originals band you probably will only do 20-30 minute sets, so can be a bunch of you r best songs, plus a couple of the less well known covers from your covers set.