I just hit level 39 (needed 9 battlegrounds), and to get to 40, I'll need to do 13 battlegrounds. I've planned out more future levels in terms of abilities and XP:
Pre-level 40: mine a lot (current mining is 361)
Level 40: Drop mining, take alchemy for a short time just to do Elixirs for the Bladeleafs quest (only need level 20 alchemy), drop alchemy, take Blacksmithing up to 200 and do the Blacksmithing quests available at 40 (over 50k XP!) I might keep Blacksmithing for a while so I can use the Glimmering Mithril Insignia. I can make good money fishing now, since I have all the STV contest equipment except the arcanite fishing pole.
Level 41: Switch Last Month's Mutton for Mug O' Hurt (with Icy Chill enchant and Crippling Poison).
Level 45: Get fishing book, get fishing up to 375.
Level 47-49: I might try to do all battlegrounds to do these levels, assuming I get two Freezing Bands (I have one now). Along with my Green Whelp Armor, anyone meleeing me has a better than 1 in 15 chance to either sleep or freeze. When I go into the 50-59 brackets, my whelp armor will no longer sleep opponents.
Level 50: Rocket Boots Xtreme! Get my engineering to 390. Do the quest in BRD to smelt dark iron, mostly for XP since I have a friend who can smelt it. Drop mining and take Tailoring to 300 so I can use Netherweave Nets in battlegrounds.
Level 55: From here on, it's remotely possible I'll be able to augment a lot of XP with....fishing! I can catch any number of Strange Engine Parts from Steam Pump Flotsam pools in Zangarmarsh. It's not a common catch, and I don't know how easy it will be for me to fish there at level 55, but once I can fish in peace, I can fish my way to 70 if I have to.