Embarking on chalk or limestone areas are among the best areas, since they tend to have magnetite clusters(more precisely known as "so much iron that I'll never need it after this one cluster is done"), and if you REALLY want to be picky, try to pick somewhere, for example, with a 4x4 embark, 1/4 of the area is chalk/limestone, and the rest having different stone layers. You'll have some variety to what stone, minerals and gems you can find on the site, but it's not THAT great really. Unless you really want to mine all those unique gems and make, I don't know, the world's most bitchin' non-artifact platinum/adamantine statue of cheese?
And if you want to take it easy for a few ingame years, why not just turn off enemy attacks from the init file? Make the fort as big as you want, get a proper military up and when you're all set, turn on invasions again.
Another piece of advice would be not to get too attached to your forts if you're not playing them to construct some sort of megaconstruction. This is a "learn from mistakes" sort of game, everytime you screw up, you tend to know why and how you screwed up, so next time the mistake won't be repeated. Burrows, unfortunately placed channels that flood the entire fort, building walls on a bridge that ends up collapsing(the wall, not the bridge) and takes down seventeen dorfs on it's way down, all legendary and socialites. There's so many ways for your minions to kill themselves and as result start killing each other, that it's ridiculous. It's not even funny.
But that's where the glory of it all really is. At least, that's the conclusion I've noticed people tend to get to once they become jaded from all that baby-murder they read and see take place.
"Oh look at that 2, that's her head. Dem dorfs, man."