Ok,, it was late & I gave a short response.
Casting is just another way to get the type & style of bullets you desire. And,,, it can save you money,,, as long as you don't value your time at a normal hourly rate.
I never consider my hobbies as a time thing,,, as I enjoy doing the things I do.
Casting slugs goes back further than jacketed ones,,, and has been done since the beginning of firearms.
If you've ever seen the Mel Gibson movie,,, "The Patriot" & where he melts down some toy lead soldiers,, over a fire, then it's ALMOST that easy. Many a pure lead ball has been cast over a Coleman stove, in a steel pot,, where the lead was dipped by a ladle, & poured into a mold.
But the pure lead stuff is soft & isn't as good as adding other metals to harden it up for faster velocities or higher pressures that handguns & even rifles use. But,,, the basics are still there. A proper mix of metal,,,, melted in a steel pot,,, OR a casting pot,,, poured by ladle or via a pour spout,,, into a good mold will give you lots of good bullets to enjoy.
I'd suggest the first thing is to buy a couple of books on casting,,, Lyman makes excellent ones. All the basics you need will be in them.
Next,,, as for getting lead,,, wheel weights USED to ALL be made of a mix of lead & other stuff that made good bullets. Unfortunately,,, the eco-freaks got the EPA involved,,, and now,,, as noted,,, the WW will be a very "hit or miss" proposition. If you go to the cast boolits forum,,, there is a lot of info on how to test the WW's to see if you can use them.
There are many other sources for scrounging lead that is suitable for casting bullets. And,,, many on that same forum sell lead they have already smelted into ingots,,, making it really easy to get good bullets right away.
But one of the more recent things that has changed a lot in casting is NOT lubing the bullets,,, but instead,,,, using a powder coating method.
And PCing a bullet is cleaner,,, easier,,, and makes for a lot of fun colors. A pound of Harbor Freight red, (only red,) with a handfull of black (only) airsoft pellets,,,, a #5 recyclable plastic tub,,, such as a Kool-whip or Country Crock (round) butter tub, some non-stick aluminum foil, and a toaster oven can turn out thousands of red coated bullets ready for sizing & shooting. No lube required.
It is truly easy to do. I had just purchased 10 sticks of an excellent quality lube to add to my depleting lube,,, when I discovered PCing. I still have the same 10 sticks new in their wrappers,,, & haven't used a lubed slug in a while.
Now,,, I've advanced a little & use a different brand of powdered paint,,, and instead of using the #5 tubs, pellets & all,,, I have tumblers I use. But I'm now converting all my cast bullets into different colors by their caliber.
Sizing a bullet is done after casting and/or after PCing. You size according to the bore of the gun you are using.
But even still,,, in this age of eco-freaks trying to eliminate a natural mineral,,, (lead) you can still scrounge up enough to make a LOT of bullets fairly easy. I'm always on the lookout for cheap quality lead or pewter (tin) for mixing bullets. As such,,, I've accumulated several hundred pounds of lead that has,, as yet,,, been turned into bullets. So,,, my cost of a bullet is extremely low. About 2-3 years ago,, I bought out a flea mkt find,,, a 5 gal bucket of OLD WW's, that the widow was selling. I gave $20 for over 150 lbs of WW's. Figure that after smelting,,, I'll have about 120 lbs or so of bullets from that alone. Or,,, the time a few years ago,,, a friend of mine was selling off his stuff,,, as he knew he was aging,,, and his family had no interest in his firearm stuff. He offered to sell his entire lot of stuff to a couple of guys,,, BUT,,, called me first. I got to cherry pick his stuff. They were there,,, inventorying things,,, and they had allowed $50 for all the lead. I told him I wanted the lead,,, already smelted into ingots,,, arranged on his shelves,,, by WW, or pure lead,,, and would buy it. (Those guys had figured .50 a lb,,, but I looked at it & knew it was a lot more than that.) I told him I'd take it all, and when I got it home, weighed it,, I came up with a bit over 375 lbs. I called him to arrange to pay him more,,, and he politely told me "No,,, keep it my friend."
So,, I'd SKIP buying lead from places like Midway,,, & start scrounging & price shopping. Get a few manuals,,, study & start casting!