Soon after buying my first Hulk comics (Incredible Hulk #167 and Marvel Super-Heroes #38), I began collecting backissues of both series as well as any reprints I could find elsewhere. I eventually acquired reprints of those elusive first six issues (Mile High Comics was asking $30 for #1!), but that mean I got them in the order of their initial publication. The first one I found was a story from #3 reprinted in Giant-Size Defenders #1. Later, another story from #3 (a linking story retelling "The Origin of the Hulk") was reprinted in Marvel Treasury Edition #5, and I acquired #3's the "Ringmaster" story in Marvel Tales #2 as a backissue.
At this far remove, I cannot recall in exactly which order I acquired the other five issues, but I know I was finally able to read #1 reprinted in Stan Lee's Origins of Marvel Comics. Before that, though, issue #2 and #6 I had serialized in Marvel Collectors' Item Classics (although I was missing the concluding chapter of #2 for a long time). I finally filled in the gaps with a little pocketbook edition which reprinted all six issues in their entirety. This is an example of what those of use who were not true "first generation" Marvelites had to go through in the '70s to fill in gaps. (I consider myself "a bastard son of the first generation" Marvelite.)
In 1978, Fireside Press released the volume I have already reference, which reprinted a large swath of Hulk serials from Tales to Astonish I didn't have, plus some other appearances as well. Before the Hulk was awarded a spot in TTA, he made a number of "interstitial" appearances (mostly) between Hulk #6 and TTA #60. Lest anyone doubt or deny we are living in a new Golden Age, allow me to remind you that all six issues of Hulk, along with the interstitial appearances from Fantastic Four #12, #25-26, Avengers #1-3, #5, Spider-Man #14, Tales to Astonish #59 and Journey into Mystery #112 are available in a single volume, arranged in release date order.
I'm going to skip those for now, but will soon begin reading the Hulk's series from when he shared Tales to Astonish with first Giant-Man then Sub-Mariner.