25 mg of Lamictal is still quite a low dose, so I wouldn't expect it to be helping just yet. (Just a caveat -- Do NOT increase it any faster than your prescriber's titration schedule, even if you feel impatient to see it work. Lamictal takes time.)

As far as not spending money, which I don't have anyway, I find not having a credit card pretty effective. (That and knowing if I can't make rent, we'd be homeless on the street -- yeah, that's a good motivator(!))

Another recommendation is to freeze your card in a bunch of water in the freezer. Inhibits the impulse factor. Not as helpful with online if you memorized your number. (If you haven't, don't!)

Is there anyone you can hand your card over to till these urges pass?

You've got a worthy financial goal. Maybe put a picture of a house in or on your wallet? And/or on your computer monitor?