Heh. those issues are a product of their time. :)
You'll find the first 4 or so Archives the same....Though a lot of Legion Lore is still introduced in those stories. The fifth archive gets more serious, with the Jim Shooter run when he brought a bit more of a Marvel touch to the stories. You'll still get some of the "childish" Silver-Age elements mixed in, however.
The 70's stories begin in Archives 10 through to Twelve. Apart from that, you should try and track down a copy of the Great Darkness Saga and the "follow up" volume which'll be released soon. Other than that, most of the original issues can be picked up cheap....That's what I did and I never regretted it. :)