Don't feel bad. It's happened to all of us. I also tried my new stock saddle--because DH said it looked cool (it was white). Nothing hurts more than road rash down there 
Definitely no underwear under bike shorts!
When I get over 25-30 miles, my "regular" bike shorts aren't enough. I've invested in some more expensive SheBeest for longer rides.
Chamois cream can't hurt to minimize friction, but isn't necessary.
Saddles--whew! I believe there is a forum just for saddles. It's a very personal choice and involves trial and error. I use a Brooks.
After chafing down there, my SheBeest shorts and Brooks saddle didn't seem like such an expense
"Well-behaved women seldom make history." --Laurel Thatcher Ulrich
'09 Trek WSD 2.1 with a Brooks B-68 saddle
'11 Trek WSD Madone 5.2 with Brooks B-17