Do you have to varnish new furniture or is stain enough?
New unfinished furniture can be finished many ways. the answer
your question will be determined by how you want the furniture to
look, how much protection will the wood need against weather
exposure ( indoors or outdoors) and how much time you are willing
to put into the finish work. Stain by itself usually will not be
enough unless the product you choose is a finish that has stain
included in the mix.