The Hunts you can start now if you're interested in getting a head start on good endgame gear. In your late 40s with the partial AF you got from your level 45 quest you should be geared well enough for them provided you also have a good weapon for your level. Spend a couple evenings running around with a Hunt party tracking down A and S rank marks and you'll have enough Soldiery and Allied Seals to get several pieces of iLvl 100 gear. (I think last time it took me about three or four evenings to get a full set. I did keep playing pretty late a couple of those evenings, though, so it might be more if you play just a couple hours at a time.) That will leave just your weapon and then further upgrades beyond 100 to focus on after you hit level 50.

(The downside of gearing up in advance like that is that your level 50 job quest rewarding your final piece of AF gear is a bit anticlimactic, as you'll already have outleveled it. Still makes a nice cosmetic, though.)