Whew! Lots to learn here.
First,,, get the Lyman casting book. It will explain alloys & such.
Lead bullets are judged by their hardness, and there are different ways to mix lead with tin etc to get what you desire.
First, decide what your bullets will be. (Pistol, rifle?)
Next, look at the application. Plinking, hunting, competition, etc.
Look at the velocities you plan to load to.
You will need to match the hardness to the velocity. (Not to throw in a monkey wrench,,, but bullet size & lubricants also come into play here as well.)
In general, many folks prefer to cast handgun bullets more often than rifle bullets. Next, if that's the desires, then in general, a lot of casual casters use straight wheelweights & do just fine. BUT,,,,,, BEWARE,,,,,,,,, All wheelweights are not created equal. There are steel, zinc, & other such crap that are not suited to bullet casting. But when you find a source of WW, you can do a testing to see if they are the lead variety, over others. (More on how in a few minutes.)
Pure lead is only good for very slow velocities & generally used for muzzleloaders.
Next, I'm going to steal a comment from sixshot here. He (as well as myself & many others,) uses a 70% lead, 30% WW mix to cast handgun slugs. Velocities are kept between 900-1100 fps for the most part, and are quite good in most applications & bullet designs. THIS IS JUST A GUIDELINE! But it works for a lot of people. Get the book & study what you need for your desires in alloys.
That said,, in general, a lot of us chase good wheelweights, pure lead & range scrap. Lynotype is great,,, but more expensive & is used to add to an alloy for most.
Costs. In general,,,, I tend to say that good known alloy such as cleaned & ready to cast WW & pure lead should be found in the $1.00-$1.25 per lb.
Now, a great place to learn a LOT is the cast bullets forum. (Also known as castboolits) You can learn a lot about alloys, how to's & whys for most casting questions & applications there. Also, many members there sell lead & you can find quality alloy's there.
Furnaces. Most of them are good, but some have a few things that make them a bit better than others. A Lee 10lb pot will work just fine as will a big cast iron pot & a dipper over a cook stove. But,,, most of us who are a bit more dedicated & do a fair amount prefer a 20 lb pot, usually by RCBS, Lyman or Hornady etc. Known names & quality. A 20 lb will get you more bullets in less time especially if you cast heavier bullets such as 200 grn & heavier. (You get it hot & casting right, use about 2/3-3/4 & you have to stop & add alloy & wait to get it up to temp. A larger pot will allow more good bullets before you start over.)
Go over to the cast bullets forum & study!