Here are some suggestions from a returning player:
1. Whatever city you're starting in you should prioritize leveling the 6 starting jobs to 12 and doing all of the quests for those starting jobs.
2. Start as war for the sword, but switch to thf> lvl thf to 12> buy dia and cure, lvl rdm to 12>lvl the rest of the jobs to 12 while emphasizing the necessary combat and magic skills for those jobs.
3. Never throw away anything. every single item that you get, save for rock salt, is either sellable on the ah, turned in for a repeatable quest, or sell to the NPC. Sell your crystals in stacks of 12, look up the quests that I have linked below, and find the quests that the items you're finding go to.
4. comments above notate crafting recipes that can leverage your starting gil quite effectively, do these.
5. once you hit lvl 12 with all jobs and do all of the quests (that don't require high level activities) in your starting town, I would recommend going to the other starting cities and doing their quests. Get the justice badge, blaze spikes, etc from windurst. Get the small sword, warp scroll, black silk neckerchief etc from Bastok. Get the friar's belt etc from San'doria. These will help you be geared appropriately for your future endeavours, and you can pick up the outpost warps and teleport key items while doing this.
6. at this point you can party in the dunes, I leveled the 5 starting jobs that I wanted to mess with at the same time, that may be more effort than you want to put in. when you hit 20 head to jeuno and pick up the gear for the push to 30. By this point you will have the items and gil to get gear for any/all classes w/out problems. I would recommend selling the blaze spikes scroll and the warp scroll (if you aren't lvling blm) and if you level the jobs that you're interested in at the same time you can sell the lower level gear.
7. Refer to the first post in this thread, At lvl 30 you are powerful enough to farm 20-30k per hour, use that to bankroll your leveling experience, spend your bcnms and excess time on ways of making large sums of gil, use that gil to level a craft and profit.
Bastok
https://ffxiclopedia.fandom.com/wiki/Port_Bastokhttps://ffxiclopedia.fandom.com/wiki/Bastok_Marketshttps://ffxiclopedia.fandom.com/wiki/Bastok_Mines Sandy
https://ffxiclopedia.fandom.com/wiki/Port_San_d'Oriahttps://ffxiclopedia.fandom.com/wiki/No ... n_d%27Oriahttps://ffxiclopedia.fandom.com/wiki/So ... n_d%27Oria Windy
https://ffxiclopedia.fandom.com/wiki/Windurst_Woodshttps://ffxiclopedia.fandom.com/wiki/Windurst_Watershttps://ffxiclopedia.fandom.com/wiki/Port_Windursthttps://ffxiclopedia.fandom.com/wiki/Windurst_Walls