For those who like to solo/duo their XP and don't want to book burn in the "big 3", here's my personnal roadmap I use on most jobs:
1-10 Zeruhn Mines, P1 or P2, level 1 to 5, can push up to 11
10-20 Dangruf Wadi, P2, then P3. Ride that till level 21
[There's a gap where there's nothing really fantastic from 21-25. You can do Dunes pages, level sync or even join the Gusgen fun a bit if you like]
25-40 Korroloka Tunnel. P1, then P2, then P3, then P4. Ride that till level 44 or so.
40-50 Sea Serpent Grotto. P1
51-60 Gustav Tunnel. P1 or P2,
60-99 Bostanieux Oublietes. P2 if solo, P4 if an alliance is burning there
For armor, I agree with the above -- starter newbie clothes --> replace by full RSE at 29-33 --> replace with full AF at 52-60 --> replace with Cruor gear at 78 and then work on real gear.
Grab your free job necklace at level 30 (plus you get the funny emote), and upgrade weapons and essential spells, if relevant.