Since you are a new rider and want good fuel efficiency, we'd recommend you stick to machines below 250cc. You have many good options in the 150/160cc commuter space, like the TVS Apache RTR 160 4V, Bajaj Pulsar N160, Yamaha FZ models and Honda Unicorn / SP160. These bikes will be light, manageable, fuel-efficient and also decently comfortable for a pillion. 

You can also take a look at sportier machines like the Yamaha XSR155 / MT-15 and KTM 160 Duke, although pillion comfort won't be a strong point on any of these bikes. 

If you want something that's a little more powerful - but still beginner-friendly - bikes like the Bajaj Pulsar N250, TVS Apache RTR 200 4V, Honda CB300F, and Suzuki Gixxer 250 models are options to consider. 

Do take a test ride of these machines to see which one suits you best.