Even though I Have done standalone oral cycles in the past, I don't think that they are the best way to go about running steroids. I feel a bit of a hypocrite saying this, but it's something I have learned from experience and now wish I would have taken the advice I am about to give sooner. That advice is, no cycle is complete without test, and if you aren't ready to inject, you aren't ready to cycle. I would take all of my standalone oral cycles back if I could now and wish I would have just done the damn thing and pinned the entire time.
However I am sure you have already made up your mind, so, I would run dbol for 6 weeks max. You're gonna want some adex to go with it to counter any gyno symptoms as dbol aromatizes.