First, get one or more reliable reloading manuals. They contain much info that you may not get anywhere else. Study & digest the processes before attempting any reloading. Ask questions of the very knowlegeable people on this Site---they are extremely helpful. And it'll save you time & aggrevation in the long term. Always be safe & conservative in your loading processes.
You'll get many opinions on what brass to buy. Just like Fords, Chevys, Dodges, etc., preferences vary. I suggest that you start out with new brass. As the "where to buy", I just buy brass locally in PA. If you check Natchez, Cabela's, Mid-South, etc., their supplies seem to fluctuate. I have also bought brass from this Site---check it daily.
I personally like Winchester for price and relative value. Yes, I've been around the block with Remington, Norma, Lapua, Federal and Hornady, but overall I get my best consistant results with Winchester. It is very tough brass
Regardless of the brass brand, I suggest that you initially inspect all brass, run them all through a sizing die, and trim them to length. Usually, I discard 1-2% for flaws. I'd suggest keeping at least one flawed/trimmed brass for as exemplary sample used to set your trimmer length.
I don't go through the process of weighing & sorting brass, but that's an option you may consider.
Good Luck!