Welcome to TFL Gunston9.
Why are some dies just for .38 but others do .38 and .357mag?
Every 38/357 die set I've ever seen will load both - and even 357 MaXimum. Maybe really old sets weren't made for Magnum? I don't know. At any rate, I there's no need to put a lot of thought into this. These days, when you buy a 38/357 die set, you get just that.
Several people have told me RCBS presses are better than Lee, but what about dies -- are the different brands comparable when it comes to dies?
I bought my first press in 1984 and it was an RCBS "Reloader Special 2." I think they're up to Reloader Special 5 now
. Anyway, I still have that press and still use it. It was my only press until a little over a year ago - when I went with a Dillon progressive for my large quantity jobs. My old RCBS RS2 is a great press and should outlive me.
As for dies, I use all RCBS - except, I do use Lee dies for some crimping operations (long story there). Bottom line: Lee dies are more economical, and probably work just fine. I spend a lot of time here on TFL; and a lot of posters speak highly of Lee dies. I have however heard a lot of people
not speak highly of Lee progressive presses. That said, I haven't heard similar unpleasantries about their single stage or turrets.
Do I really need a tumbler cleaner?
No. I went without for a couple decades. I just cleaned them in a bucket of dish soap n water. But they don't come out pretty. At any rate, a tumbler is not a necessary piece of equipment when just starting out.
What IS a necessary piece of equipment is a reputable manual on the basics of ammunition loading. Do you have one of those? Often recommended include Speer, Hornady, and/or Lyman. It's important to read up before getting started.
Which leads to more questions: Where are you in the world of handloading? Just thinking about it? Committed? What calibers are you planning on loading (38 Special and/or 357 Magnum, evidently
)? For what purpose? These are all things we'd like to know in order to answer your additional questions in more detail and direction.
Again, welcome aboard.