IS IT ABSOULUTY NESSESARY to add gravel from a cycled tank?
No, it's not necessary at all to add gravel or filter media from an established tank, but it will generally speed things along significantly if you do. This is true regardless of how you cycle (with or without fish). The necessary bacteria will colonize and your tank will cycle without adding any seed bacteria at all, though. It will just take longer.
As much or little as you like. Generally speaking, the more seed material you add, the quicker the cycle will go, but this is not a universal law. Even a little seed material will generally speed things along much better than starting with none. Also, be mindful that the more seed material you take from an existing tank, the greater a "cycling deficit" you're creating for it to overcome. This is generally not a problem, but it's certainly possible to overdo it sufficiently to cause problems in the established tank.
what would the time frame be for adding fish?
However long it takes. When the cycle is finished - not before. There's no way to guess when that will be. Cycling fishlessly is usually faster, but it can still vary a lot. Remember, impatience is the enemy.

You cannot schedule the completion of a tank cycle. It's safe to add fish when your water test results indicate the cycle has completed it's final phase (i.e. nitrite spikes for a period of days and then falls to zero) and parameters consistently indicate cycled tank behavior for a couple of days (i.e. ammonia is zero, nitrite is zero, and nitrates rises steadily).
pendragon!