Most of the sight in problems I see are related to scope mounting. either loose mounts, bases, or rings. With a cheap scope, you might also have a bad one that won't hold zero. Degrease and use blue Locktite when you mount the scope, and when you get it zeroed, test the scope for repeatability and make sure it holds. You might also check the rifle for some major problem, a bad crown, out of spec barrel, or something.
Boresight, either with a good optical bore sighter or through the barrel from a good rest. Shoot close and then move out.