CP is brutally hard for tyranids. You have pretty much two choices: Genestealer heavy, or warriors and little things. Genestealer Heavy doesn't have enough models to make it to the enemy EVER, and warriors+little things just doesn't have much of a punch, and will be shot up again.
My suggestion is to do 500 points (which we're still bad at, but not as awful) if you need a quick game.