#1
I hope is in the right place, well I have an Ibanez GIO GRX40 and specially the 6th and 4th strings makes a buzz even when I play those open, If I play lightly it doesn't buzz, do I need to change the strings? adjust the guitar? or why happens?
#2
I had this problem lately with my carvin, on its e string. Its usually because of nut height, and the neck bow. You will need to adjust your truss rod probably. Hold the body of the guitar and look down the neck from the top of the headstock. Is the neck bending backwards, forwards, or perfectly straight? If backwards, you will probably need truss rod adjustment.

The reason it is to do with these things is because your string is extremely low to the frets and the strings are vibrating against the 1st fret. You won't specifically get this buzz on upper frets, but on open strings this can occur.
#4
http://users.powernet.co.uk/guitars/setup5.htm

this is the guide i used, gave me the general idea of what i had to do. There shouldn't be a truss rod cover on the ibanez gio, so you can probably see where it is near the nut. Make light adjustments and wait for the adjustments to settle. I'd do this with the strings off, so you get a better idea of what your doing and what adjustment you have done.
#9
It could end up being technique, or the overall quality of the guitar (which isn't incredible with a GIO lets be honest). I would let it fly by unless it is extremely prominent, and hell, if this is your first guitar and your learning, you want to learn to play clearly and have good technique, rather than fuss over a small bit of buzz. Unless its a serious problem which will stop you playing it, then i wouldn't bother.