Way to help out, guys.
Cxplorer, first of all you need at least R25 to get your own Chocobo.
Once you achieve that rank, go to every city state and become a recruit on the Grand Companies by doing their quests until you get these quests:
Till Sea Swallows All (Maelstrom)
Serenity, Purity, Sanctity (Twin Adder)
By Fire Reborn (Eternal Flames)
These are the GC speech quests, which you must do in every city-state too.
When you're done with all these quests, you should choose one of the grand companies to pledge allegiance.
You'll be given a new quest from the grand company of your choice and by the end of this quest you'll become a Private Third Class which will enable you to buy a chocobo for 3000 seals.
Grand Company Seals can be obtained in many ways (Grand Company leves, Caravan Security, Quests...)
Hope this helped.