Acqueous cream is by far and away the best and cheapest product to use as a shaving gel / foam / oil. A few dabs cover your face, keeps your skin happy and slippery, and doesn't stick to the razor blades beyond a quick rinse with water. A large tub costs a fiver, and lasts a year.
Why not just use shaving soap? A bowl will last forever and refills cost a couple of bucks.
In general though, I highly recommend moving to single-blade safety razors if you haven't already. You just buy them in packs of 100 so you aren't stuck with Gillette etc's bullshit business model. It saves you ludicrous amounts of money in the long term. Plus, if you happen to have an issue with razor burn or bumps, switching to a single-blade is by far the best way to deal with them.