10-12lbs a year if you get everything bang on.
Fluctuations in weight will be due to volume of food & fluid ingested, bowel movements, water retention, drops/increases in bodyfat, muscle gain etc.
When on a Keto cut about a year ago I my weight would drop 2KG overnight. I was urinating like a race horse though. Generally during this period I would drop .2/.3KG every 2 days or so.
I wouldn't watch the scales when you're trying to gain weight it's not a clear indicator. Weigh in once a month, obsessing over scales will leave you confused and unnecesarily disappointed.