What should I get first garuga weps or armor?

Make the armour the weapons arent that great

With a fire or water artib weapon if possible

Get the armour first, then you can last longer against harder wyverns.

I recommend anything fire, but I doubt you can get the materials to make a fire wepon yet. So I recommend the SnS either viper bite or hydra bite. You need to take enough whetstones with you though. With an SnS all you need to do is run in circles around him. Let him make the first move, so if he spits poison for example, then run behind him and hack at him, then roll away and continue running in cirles around him. This is a very effective tactic, as the gypceros will only hit you if he is lucky. Unless he hits you with his tail. After he has finished one move, I tend to stay just the left, behind him, so if he swings his tail, I have enough time to move out the way. The tail is the most annoying part of the gypceros, because it reaches further than it looks.

Watch if he plays dead too, because that will do considerable damage to you, if you get hit by it.