Well if you are uncertain how to level, for the levels 70-90 i usually prefer questing. There are a bunch of low level quests who don't give to much exp on your level so you won't get to waste that exp. Examples of those are;
With credit to Spirit who wrote this guide, i only posted this part of the quest guide but there's more if you're interested.
SoS Wrote:The #'s are used to show difficulty. Reason for difficulty varies, fights, locations, items, ect.
60+
-Hide n' Seek Quest?? #
(250,000 Base)
-Hugel Memory Quest?? #
(250,000 Base)
70+
-Shadow Job Quest?? #
(7,000,000 Base)
-How The Airship Works Quest?? #
-Heart Fragment Quest?? #
(4,500,000 Base/2,050,000 Job)
-Crow of Destiny Quest?? ##
(4,500,000 Base/4,500,000 Job)
-Finding the Moving Island Quest?? ##
(6,000,000 Base)
(Moscovia Field Access)
-Medicine Quest?? #
-Biological Weapon Quest?? ##
(6,250,000 Base)
-Lost Child Quest?? #
-Rachel Sanctuary Quest?? ##
-Veins Sibligns Quest?? ####
-Curse of Gaebolg Quest?? ##
-Nameless Island Entrance Quest (entrance/complete)?? ##/####
(23,000,000 Base/6,500,000 Base) + (7,500,000 Base for complete)
(Nameless Access)
-Thor Volcano Base Quest?? ###
-Peace for Arunafeltz?? ###
(17,500,000 Base)
-Ice Necklace Quest?? ##/####
(3,500,550 Base) + (Ktullanux Exp)
-Kiel Hyre?? ##/#####
(3,500,000 Base) + (5,000,000 if you kill him after)
(Robot Factory 1 Access) + (Floor 2 access if you kill him after)
-Onwards to the New World?? ###
Otherwise, if you have any elemental katars then leveling on places that are suitable for those katars might help you a lot. Such as hillwinds with an earth katar etc. Hill winds is pretty good exp and decent loots, if you don't have an earth katar you could hunt one at Sandman and gain both exp and the chance to get an earth katar. Best way to do this would be with an fire katar which are usually 250-500K a piece.
For zeny you could just farm items such as stems to sell to creators and such. Finishing your Beewings is a good idea to get more zeny as well.
Hope this helps a little.