Excellent post by Estellios, to recap :

Conjurer lvl 34 to get
1- Cure (lvl2)
2- Protect (lvl6)
3- Raise (lvl18)
4- Stoneskin (lvl26)
5- Prism (lvl34)

Pugilist lvl 6 to get
1- Featherfooted (lvl2)
2- SecondWind (lvl6)

Gladiator lvl 22 to get
1- Rampart (lvl2)
2- Sentinal (lvl22)

Lancer lvl 14 to get
1- Invigorate (lvl14)

Archer lvl 42 to get
1- Chameleon (lvl42)
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Keep in mind that you dont need to have all these skills to join a lvl50 group.

However, I would recommend getting the ones from CNJ and PUG, if you have extra time get the ones from GLA and you will be set to go.