To estimate how long will take to get a block mined you can use the following calculation (it's not sure, it's probability):

time in hours = difficulty * 2^32 / your hash rate / 3600

For instance, if you have 1GH/s rig, assuming the Digibyte difficulty stays at 10,000 for long enough to find a block, you will mine a block in average every 12 hours.

10,000 * 2^32 / 1,000,000,000 / 3600

Consider that the difficulty of Digibyte lately is jumping quite a lot... if you don't have a decent hash rate don't solo mine. 1GH/s it's already borderline, below 1.5 or 2GH/s I would not solo mine.