The answer is It Depends.
If you are shooting low pressure pistol like .38 special or .45 auto then a softer alloy like 50-50 wheelweight and soft lead would be fine.
If you are talking faster stuff like 9mm or .40 or +P .38 then an alloy of wheelweights +2% tin would be good, and you can water drop them. 80-20 wheelweights and type metal works good too.
If you are talking fullbore Magnum pistols or rifles with cast load data then using straight type metal would be hard enough.
With cast boolits the important thing is to make the bullet size large enough to fit the bore tight and use good lube.
My advice is to grab any lead you can find, focus on finding wheel weights (they have antimony in them usually, and that's a PITA to add to lead otherwise). WW lead can be hardened and it's great to cast from. Also look for type metal (linotype, monotype, foundry type) or solder or babbitt metal anywhere you can find it (for tin). Soft lead is still used a lot but it needs to be toughened up for most smokeless powder boolits.
Bear in mind lead took a sharp upturn in price and is over $1 a pound right now. If you can find any lead for less than 50 cents a pound, grab it.
Be advised the wheel weights are being replaced with iron or zinc weights so a bucket of wheelweights may not be all lead! The stick-on weights are nearly pure lead, keep them separated and don't melt them in with the other clip weights (it's easy to add later on, impossible to separate once melted!)