Starting from your starting zone, Archet for Hobbits/Men and Duillond for Elves and Thorin's Gate for Dwarves.
1 - 15 : Starting region. Should be enough quests for you to do to reach 15, if not travel to starting zones of other races and do the green/blue quests
15 - 17 : Bree-land
17 - 21 : Forsaken Inn in the Lonelands or the Great-Barrows quests
21 - 25 : Start questing in Ost Guruth, and often try to get a group for Great-Barrows
25 - 30 : North-downs, complete quests around Trestlebridge
30 - 35 : Should bring you to around Esteldin now. Complete quests around here.
35 - 40 : Before Evendim, this was probably the hardest grind. Anyway, complete quests around Rivendell, MM, Trollshaws, and of course Evendim
* Fornost is a nice instance to do if you can get a group. Also, start doing MM around 39+
40 - 50 : Now, you really have no choice here, it's Angmar and MM, start off in Western Angmar and work your way east (to get into Eastern Malenhad you have to complete Book 5/6)
EDIT : I'm an idiot