This was reality for me. I turned 10 in November 1972 and started watching Trek sometime that Fall. By the mid 70s I had purchased at least two AMT Enterprise kits, the Klingon cruiser, the Spock kit, the shuttlecraft, the bridge diorama, the Romulan ship, the K-7, the Exploration Set, even the "Interplanetray UFO" kit (the Matt Jefferies designed Leif Ericson ship repackaged), really, the entire AMT Trek line.
I bought the Mego Spock doll, first one with the metal rivets and later a second with the plastic joints. (I converted the first one into a WestWorld type android by cutting off his face and stuffing the cavity with a wad of wire.)
I had James Blish's "Spock Must Die!" and the 5th volume of his episode novelizations. When Alan Dean Foster started releasing his adaptations of the animateds, I bought those as well. (I eventually got all of those by 1980.)
As for "reference" material, I bought the deck plans by Franz Joseph and later his Tech Manuel. Trimble's Concordance? Yep, grabbed that. And like any diligent Trekkie of that era, I had Whitfield's "Making of Star Trek" and both of David Gerrold's "behind the scenes" paperbacks, "Making of...Tribbles" and "The World of Star Trek".
What I did NOT get were any of the Mego brand electronic toys like the communicator walkie-talkies or the tricorder tape recorder. I did buy the Remco "electronic" phaser, but I wish I had not. That thing was a "rip". I expected the sounds we now have in the Art Asylum toy/props. Instead, when I pulled the trigger, it chirped like a bird! Boy, was I pissed!
I think that about covers it. Shoot, looking back, I was a bit of a collecting fool!