When I was levelling for the first time, every time I got a certain threshold on Gil, I put it on the retainer. IIRc was 20k gil, albeit back then Gil was harder to make, no gil drops from fungeon mobs for example. Which kinda made me not TP and not buy things XD As I was trying to get to those thresholds to bank more gil. Got to 50 with around 1 or 1.5 million the first time. Habit I still do today, over 100k Gil, I bank 100k on the retainer.

Don't buy gear from the MB for levelling, use GC seals, or run the dungeon at your level a few timse for more gear. Also check leves for gear upgrades, and while doing leves always check the area incase theirs a bonus chest.