Start by asking the most specific questions you can. General “what’s it take”, gets a variety of information that may or may not be important.
There are a bunch of us here that cast and a number of us are also member’s here
https://castboolits.gunloads.com/ where the discussions of cast bullets often gets more in depth.
For question #1 As far as coefficients of friction, a lead bullet will cause less wear than a copper/alloy jacket will and its not uncommon to be running them at lower pressures, that extends the life of everything.
#2, lower velocity, “odd ball” rounds are often the best because the “odd balls” would be the most expensive to buy, saving you the most money/per hours spent and the lower velocities helps with leading, if you are not coating.
First thing I would try and figure out is what you want out of it. Are you wanting to craft your own precision, long range rifle bullets? Swaging, might be a better choice, unless you just play cast games.
If cheap is a goal, how are you going to get and deal with your lead. No telling how many times I have fired some pieces of lead but I have traps that catch my bullets, so I just melt them down and put them into the shapes I need. If you have to buy lead, that may be a deal breaker from the start.
In any case the process of casting and shooting bullets is as safe as you are. No different than reloading in general, from that stand point. You just control more variables in the process than most.