If you're looking for cheap performance you're not going to find it. Even before tweaking the stock ecu I'd look at Stillen's axle-back or cat-back exhausts. Uncorking the airflow on a forced induction vehicle is one of the cheapest and easiest ways to make safe & reliable power. I'm hoping that eventually Cobb Tuning steps up and makes an Accessport for the Juke, but I don't see that happening anytime soon.
Something I say a lot in the Z forums - one of the best modifications you can make for immediate performance improvement is good tires. The Goodyear F1's that came on the Juke aren't bad, but they're all seasons and if you can swing an extra set of wheels and load them up with summers it will pay off huge in extending the life of your all-seasons with the added bonus of a huge performance boost when you can run them.