Whatever you want. Do you *need* any plans? Definitely not. They're all nice for now, but the good ones are still 50-100m and it's debatable if you're willing to pay that much for a potential sidegrade/upgrade (it's not even guaranteed the crafted item will turn out great).
No level 60 plan is gonna be super essential on level 70, so other than for achievements, personal goals (get all plans), or wasting some gold on stuff that becomes obsolete in 15 days there's absolutely no reason to go crazy and buy anything.
No level 60 plan is gonna be super essential on level 70, so other than for achievements, personal goals (get all plans), or wasting some gold on stuff that becomes obsolete in 15 days there's absolutely no reason to go crazy and buy anything.