What do guys think I should buy for production and mixing ? Is expensive headphones a good choice or a decent pair of monitors would do? I have heard for production you need Monitors and for mixing/mastering purposes you need headphones but at the moment I can afford only one of them.What should I buy?

If you live in a place that allows it, then monitors for sure.

Really depends on the monitors you will be buying. Monitors usually dont have the frequency range for sub basses so it will be really difficult to mix. I suggest as starting out get the really good headphones that have a flat response so that you can really hear what the true sound is.

I would personally suggest getting a good pair of headphones. They'll run you about the same price as one speaker. Plus by the time you save enough money for monitors you would hopefully have done an incredibly insane amount of mixing on your phones, so that you can use them in an efficient manner. Not to mention you know what to look for when learning your speakers and how stereo imagine works if you spend a solid six months (over kill but eh) only working with headphones.

But honestly, i think for most people (including myself) you won't get the full picture until you actually drop some coin on the lowest high end gear you can get your hands on. i wouldn't go below the 350 dollar range on speakers and the 300 buck range on headphones. that's when you start getting into big boy land.