Assuming you're quested, you could most likely swap the Zerk for a maxed account and some RSGP. That will save you a lot of time, and you'll gain cash.
If you want to train the account you have, Armoured Zombies might be the best option.
Also, if you don't already, do Troll Invasion once a month. If you aren't putting the XP into anything else, you might as well use it on combat. Great XP for like 10 minutes of killing stuff.