Personally I would try and get more test and run that. But I've heard good things about the 'classic' d-bol/deca cycle. It will be especially good if its your first, although I would prefer test/d-bol/deca, test/deca, or test/d-bol. I ran a test/deca/d-bol cycle for my 1st one and gained 30 lbs. Kept 16 of it with no PCT. But to answer your question, I would guess you could easily gain 15-20 lbs., maybe even up to 30.
If you stick with the deca/d-bol go:
1-5 or 6: 20-30 mgs. d-bol a day
1-10 to 14: 300-400 mgs. of deca a week
duration of cycle: 10-20 mgs. nolva a day
Clomid/nolva PCT
Deca builds muscle gradually over time, so the longer you stay on it the more you'll gain. 10 or 12 wks. should do the job, but you can go up to 14 if you want.