My first big-time concert was a good one - Led Zeppelin at the Chicago Stadium (where the Bulls played prior to the United Center opening up next door), during their 1973 tour. I had just finished high school. I don't know if the fifth album (Houses of the Holy) was out already, or just about to come out. So they played a fair amount of that. But they also played almost all of ZoSo, most of LZ II, and lots of 1 and III. Just a great show.
Prior to that I had only gone to smaller shows of local bands, etc. But I remember that there was a summer concert series at the Dupage County Fairgrounds, probably the summer of 1972 (but I may be off by a year), where you paid $2. The venue was the 4-H exhibit hall, which was more or less like a middle-school "multi-purpose room", with the typical school stage that's raised 3 feet off of the tile floor. No seats, so you stood, or sat on the floor (if possible). That summer, for $2 a show, I saw Styx, Wishbone Ash, plus this new band that I'd never heard of, called Electric Light Orchestra. Their first real radio hit, "Roll Over Beethoven" hadn't come out yet, so I literally knew nothing about them. It was completely amazing to see a band with a violin player who wore a cape, a cello player who wore this sort of monk's outfit, and then the rest of the band looking more like rock stars (including Jeff Lynne in his gigantic afro days!) When they launched into an extended version of "In the Hall of the Mountain King" (aka the song from the "Sorcerer's Apprentice" section of Disney's Fantasia), and just kept playing faster and faster, the place went nuts!
College was when I really started going to more concerts, but that's for another thread...