I've gotten my new Inquisitor alt 95% to level 51 in less than a month just through solo questing and very little XP grinding in a group. There's a ton of questing to do. If you're in your low 40s, I'd tell you head to Zek, Steamfont and the Feerrott and do the plethora of questlines there. If you want some help after that, there's a page on the EQ2i site with solo questlines that'll take you all the way to level 80.
http://eq2.wikia.com/wiki/Category:Solo_Timelines
Don't overlook those green quests, though. If you're looking to get the most bang for your buck, do every soloable quest you can that cons green to you. For no other reason, you'll be getting AA experience and we all know how monumentally important a decent AA spec is to get the most out of the class. If you really want, push through those grey ones, too and find a lowbie to mentor before the turn in to get credit.