yeah, if you wanna start with Fantastic Four #1 and keep reading FF as long as you like, there's the Essentials, the Masterworks, and the CD-Rom, that's easy to get you started on. But if you want to do strict "in order", it would be something like (and this is NOT the correct order, I'm just guessing):
#1 FF #1
#2 FF #2
#3 FF #3
#4 FF #4
#5 FF #5
#6 Hulk #1
#7 FF #6
#8 Hulk #2
#9 FF #7
#10 Tales of Suspense #38
#11 Hulk #3
#12 FF #8
#13 Tales of Suspense #39
#14 Journey into Mystery #86
#15 Amazing Fantasy #15
#16 FF #9
#17 Hulk #4
#18 Tales of Suspense #40
#19 Journey into Mystery #87
#20 FF #10
#21 Hulk #5
#22 Tales of Suspense #41
#23 Journey into Mystery #88
#24 FF #11
#25 Hulk #6
#26 Amazing Spider-Man #1
etc. etc. and so on and so on, with more and more titles being added, and you'd have to jump from one to anotehr to another to another over and over again since they all, technicly, happen in between each other.
So, assuming you didn't actually buy the original copies which would run you thousands of dollars, you'd have to get about a dozen books that reprint the old stories to start with, and read one chapter in one, then read one chapter in another, then one chapter in another, then the second chapter in the first book, then the second chapter in the second book, and so on.
The sensable thing to do would be to read, say the first 30 issues of the Fantastic Four, which is available in one volume, then jump to the first thirty issues of whatever interests you next, say Spider-Man, then Avengers, Hulk, Captain America, etc. But really, the goal of reading everything strictly in order is daunting even if you're already a major fan.