After reading this I am pretty sure you're asking where to buy gear at level 30. But then the topic threw me off because it's not an potd issue? So I am going to answer both because maybe I just can't read today lol
If you're still leveling or planning on leveling via potd, you won't need any gear since the potd system doesn't apply it. All you need to do is, level your armor and weapon stats with repeating the lower level floors 1-49. Some people just run 1-20 over and over till they reach something around 30+. And while potd let you enter the higher floors with weapons/armor stat of 16+ it's not something I would recommend. Especially since floor 51 seem to attract alot of speed runners and you won't be able to "compete" on/with their level.
For outside of PotD, after you've reached level 30 check your servers market board if you have not leveled your own crafters. Depending on the server itself, you can find easily some HQ (28-30) pieces that won't cost much. If you still don't want to invest in that, check your grand company, you can get a couple of pieces there as well that are level 30 green equipment. Now if you are feeling very adventures and don't want to invest a couple of gil, run haukke manor and hope for drops (lvl 28 pinks). These would last till level 32 at least, and you could continue farming brayflox. That gear is enough till around 35/38 and you can move onto sunken temple of bs lol. etc.
Another method would be leveling in potd all the way to 45 and picking up the free job gear from your job quest. Same at level 50 and continue your quest/msq if that still applies to you.