Just hit 30, time to start leveling the other class.

Before I start I want to say that I did read the similar post on this page. However, I had some other questions that may not have been related to that post so I didn't want to hijack it.

I'm going for Dragoon so I am curious, can I continue doing my story as a Lancer or do I need to stop now for DRG?

I know I can get skills from Archer, Pugilist, and Marauder but how far do I need to take each class? Should I get all my cross class skills possible before switching back over to my Lancer/Dragoon?

After you do your level 30 lancer quest your lancer quests are over. They are now all dragoon quests. You cant use archer cross class skills. If you want to be very particular get marauder high enough for mercy stroke and pugilist high enough for mantra. Can't remember the levels on either

DRG and LNC level at the same time once you unlock DRG and generally you should proceed as a DRG (if that's gonna be your main) since from 30+ you're expected to deal damage very efficiently and you can do that better as a DRG than you would as a LNC.

For your second question: It honestly depends on each skill you stand to gain but keep in mind DRG has a smaller pool of cross class skills to choose from in exchange for their job specific damage abilities.

the only time lancer would be better then dragoon would be if you have a lot of other classes leveled up a bit and want equip skills that the lancer can, but dragoon can not such as heals or stone skin. otherwise the job's are just flat out better versions of the classes and should be freely used. so. imo, you should at a minimum take 15 levels of murauder to get dragoon.

you do not however, need to rush to get all the available cross class skills. some of them are useful, but rarely vital to playing your class/job.
in the case of dragoon it seems most of the cross class skills add either a little damage, or self healing.

http://www.ign.com/wikis/final-fantasy-xiv/Dragoon has a list.

Just to let you know, DRG can't use anything from Archer.

Just be aware that Dragoons do not have all the cross-class abilities that a Lancer has (as Estellios points out). See this link for details on DRG cross-class abilities and their levels. To get them all, level MRD to 26 and MNK to 42 (yup, another 30 levels just for Mantra - but its an awesome ability).

Thanks everyone! The wiki I found had some archer abilities too sorry for the misinformation. The marauder to 26 isn't too bad. But wow I may as well max out monk lol