Some good advice already here.

It depends on what kind of melter you have, if you're starting out with the little Hot Pot 2 you may have problems getting wheel weight lead hot enough to get a good poor in your jig mold.

I suggest starting out with pure lead, it's the easiest to work with.

If you get serious about pouring jigs I highly recommend the Lee Production Pot 4. it has a temperature control and will make it easier to pour with hard lead alloys.

If you need a good source for lead, these folks are great to deal with.

Casting Bullet Alloys from Rotometals