If you're just EXPing, there's not really much to worry about. You obviously won't have the confluxes for whatever area you're in, so if you need a guide, don't hesitate to ask someone in your party. You should perhaps let your leader know beforehand, too. I doubt you'll get uninvited, but hey, sometimes people can be pricks.
Assuming this your first trip for EXP purposes, you'll want to save your cruor to unlock the aforementioned confluxes (they're like warp points within the zone) and then to later be able to buy things like abyssites and maps. I forget if you're given a bit of start cruor for your first time, but you'll want to at least pick up the MP buff to help your longevity a bit.
Once you've got a healthy stockpile of cruor, you'll want to buy the Celerity abyssite from a Heroes zone (Ule, Altep, Grau). This will cut the amount of time needed to replenish a traverser stone from Joachim. You can also gather various pop items from the AH to do a repeat quest in Vunkerl that can then get you another Celerity abyssite. The third and final one is acquired randomly from killing Tonberry in Kon. You must be the puller to receive it, as well.
Now that we've upped how often you can enter Abyssea, you'll want to look into getting Atmas. I have no clue what your mission progression is, but if you're rank 10 in Windurst, you can buy a synthetic Atma with +5 Refresh and a minor MATK boost. This can hold you over with the Lunar Abyssite you can by from a Heroes zone for 100k cruor. Alternatively, if you pay attention to shouts in Port Jeuno, you may be able to score a PUG for a random zone boss kill. Your first kill of the 9 will also grant you a Lunar, with the third coming from the 7th kill. Noteworthy Atmas for a more mage-minded RDM include the Windy one I mentioned, Minikin Monstrosity (red trigger from Durinn in Vunkerl), Beyond (red trigger from T3 VNM in Kon), Ambition (synthetic for clearing ASA), and Ultimate (synthetic for beating Ultima Weapon in Limbus).
For more info on Atmas, check here
For more info on Abyssites, can check
here. You'll probably wanna mix and match wiki info to get more details on various ones, though.
Finally, while I didn't throw the maps and such together, I did throw this zip together
to make life for my LS easier. Aside from the newer zones, they're pretty much accurate.