It sounds like your body and confidence will get healthier the longer you stay away from smoking. Congrats on getting started. It's hard to say how long it will take you to gain weight. That depends on your body, how many calories you consume and how many calories you burn. It sounds like you are already making quick progress though.
Keep us updated on how you are doing. I am looking forward to reading about your progress.
I guess the weight gain will depend on how long it takes for your metabolism to adjust and your appetite to recover. When I stopped all nicotine, I got very hungry. Blood sugar levels were all over the place, since nicotine can artificially increase blood sugar. So when I no longer had the nicotine, I would feel sudden and painful urges to eat a lot. I suspect that I gained a few pounds in that first month, but I didn't really look at the weight issue until much later. My priority for about a year was just keeping my quit.
I know I gain weight when I quit. I lost 30 pounds when I started smoking, all within 1 month of smoking after I quit for 3 months. In that 3 months I gained that 30 pounds. Its important I gain 30+ more pounds this time again because I am 104 pounds, 20 years old, and 5 foot 8 inches tall. I'm severely underweight.
I never counted the days till I saw weight gain. I can see my ribs right now, my arms are so skinny my wrists look like a baby could stap them. I basically look like a crack head. My friend calls me a cancer patient with hair as a joke because I'm so skinny. I find that pretty insulting because im somewhat self conscious about my weight right now since I'm so skinny due to me being a smoker (ex-smoker now) and my muscles are so flabby and weak as well. I did quit 6 days ago and have been working out. My muscles are gaining hardness. Before I quit my bicep and triceps had no definition and looking at myself in the mirror i told myself I had noodle arms. Now that have definition and are more rounded, and have definition. As do my pecks and abs.
I'm wondering how long it typically takes for ex-smokers to notice weight gain. I was 104 pounds last time I weighed myself. I will weigh myself when I quit for 1 full week to see how many pounds per week I'm gaining. I see a little gain in my forearms and upper arm. My rips are something I'd like to not see, they just make me look really skinny. People think I don't eat or that I have that eating disorder where people puke after eating, or just simply don't eat. Its not true at all.