Well kinda depends. Cheap is an ALICE external or Condor 3-day. Sturdy for 60 lbs would be ALICE external, Go Ruck, MR, Crossfire, etc. Getting both might be tough.
For exercise, especially light jogging, the Go Rucks excel. They are designed for iron plates and carry them well. So if this is what you're doing, I'd get into a Go Ruck as soon as possible.
For rucking with an actual load, I would start with a good external like the ALICE and then invest in a good upgrade if I wanted to continue. For me that would be a Crossfire frameset, with bag of your choice (ALICE, ALICE mod, FILBE, Molle Large, Molle 4,000).
I have rucked the Crossfire DG-16 frameset with the jarhead FILBE bag and it works pretty good. You could start with the 1606 frame, but I think you'd want to upgrade pretty quick.
You can use the waist belt, or remove/tape it up. Gonna depend on the weight and duration of the work out. For heavier loads, and longer distances, I will use the waist strap, unless I have a belt kit for it to rest on.