I would say re-gear, for the following reason.
if money is an issue, it won't get any better spending money on a locker, and still spending more money on your milege until you save up again for a gear install.
yes it costs more to re-gear, but the sonner you do, the sooner you are able to put away a few more dollars until you can get a locker too.
granted if this is a trail only rig and your ok with the current gearing (not too bogged down) than go for the locker so you can go a little further, maybe break a few more parts (you'll be hitting the gas more with stock gears) and you can save up all over again for more parts.
I re-geared mine, than locker, and very glad I did.