There are a lot of gylphs to chose from, some of which are very situational and are only ever used in specific circumstances. There are, however, 4 Glyphs which are standard for Resto Druid PvP in Arenas.
These Glyphs are:
Glyph of Cyclone - Increases the range of your Cyclone spell by 5 yards.
Glyph of Efflorescence - The Efflorescence effect is now caused by your Wild Mushroom instead of by Swiftmend, and lasts as long as the Wild Mushroom is active. Additionally, increases the healing done by Swiftmend by 20%.
Glyph of Regwoth - Increases the critical strike chance of your Regrowth by 40%, but removes the periodic component of the spell.
Glyph of Barkskin - Reduces the chance you'll be critically hit by 25% while Barkskin is active.
The Glyphs that you will always want to use are Glyph of Cyclone and Glyph of Efflorescence. Having additional range to Cyclone is extremely helpful because the baseline short range on Cyclone makes the spell very easy to outrange by competent players. The Glyph pairs nicely with the PvP glove bonus and is a good offensive asset for your team. Glyph of Efflorescence is essential because it increases the healing done by your strongest short CD burst heal. When using this glyph, it is reccomended that you pair it with the minor glyph: Glyph of Sprouting Mushroom as this glyph allows you to micromanage the use of your mushroom and its AoE healing effect.
Your third glyph slot will either be Glyph of Regrowth or Glyph of Barkskin. You will want to use Glyph of Regrowth if and only if you are certain that the enemy team will not make swaps to you. Glyph of Barkskin is essential for surviving swaps. You can negate a lof of offensive pressure from the enemy team with this Glyph alone. Glyph of Regrowth is very powerful in Warrior/Mage/Druid mirrors and against teams which do high burst damage to your teammates.