My original collection from when I was a kid in the mid 60's to mid 70's included these titles with unbroken runs of issues,
Amazing Spider-man #63-149
Aquaman 34-45
Avengers 54-140
Batman 199-223
Brave and the Bold 72-103
Conan 1-24
Daredevil 42-70
Defenders 1-28
Fantastic Four 68-150
Flash 172-218
Green Lantern 54-89
Iron Man 4-53
Justice League of America 54-106
Kamandi 1-17
Marvel Team-Up 1-20
Metal Men 20-41
Mister Miracle 1-18
New Gods 1-11
Silver Surfer 1-18
Sub-Mariner 4-37
Superboy 141-166
Superman 199-258
Thor 160-173 and then 200-240
X-Men 53-66
I collected other titles as well like Action Comics, Adventure Comics, Captain America, Detective Comics, Doctor Strange, Forever People, Metamorpho and Nick Fury to name a few, but only picked these titles up sporadically. Some titles like Iron Man and Sub-Mariner I had both issues of #1 but missed issues #2 and #3 and picked up again with issues #4 and continued on. Same with Thor, I had #150 but didn't buy another copy until #158 and then picked up again with #160.