How to Fast Level up FFXIV Secondary Class

As we know, FFXIV (ranks No.3 of the top 10 MMORPGs in the game virtual currency market 2016) has a secondary class which is totally different from any other MMOs. Now, there are 13 jobs, each job has each secondary class (Warrior-Gladiator, Paladin-Conjurer, Monk-Lancer, Dragon-Marauder, Bard-Pugilist, White Mage-Arcanist, Black Mage-Archer, Summoner-Thaumaturge, Scholar-Conjurer, Ninja-Pugilist, Dark Knight-Gladiator, Astrologian-Conjurer, Machinist-Archer).