Caitiff

Right, so I've got a current agility level of 43, and I'm trying to get it up to 50. I've been training at the Barbarian course, but it's painfully slow and I dislike it.. I know there's the Agility Arena but I find I fail too many of the obstacles so my lobsters get used up fairly quickly.. I've got a good budget, so I'm wondering, what should I do to get my agility to level 50 quickly?

Well, I usually have like 10 favorite songs at a time, but right now my favorite song is "Fix You" by Coldplay.=)