While I am no expert, when I was researching what birds I could get to join my 2 budgies, I realised that it is very risky to keep budgies and ringnecks together, even if they are housed separately and only spend time together out of the cage. While there are cases of ringnecks and budgies getting along okay, ringnecks are much larger (over double the size of budgies) with much larger beaks, and if provoked can cause serious (even fatal) injuries to a small bird like a budgie. Budgies can get a little territorial and aggressive sometimes depending on the bird, and this cheekiness can definitely provoke other birds.
I have a cockatiel, and many people have success with cockatiels and budgies. Cockatiels (particularly females) are very relaxed and mellow. They also aren't as large as ringnecks. When my budgies annoy my cockatiel, she never reacts with more than a hiss.
All this being said, as others have pointed out, you never really know. A ringneck and your budgies may very well get along - but keep in mind that it is quite risky.
Good luck!