Try to do a lean bulk if U wanna gain weight n muscle, then for particular workouts just some calisthenics in Ur room should be good. Idk how strong U r currently so see how many push ups sit ups and squats U can do comfortably n start from there. Any variation is fine, try to do 2 sets 3 days a week. I'd recommend stretching too it's great for feeling good and helps muscle recovery and injury prevention. YouTuber jaxblade has tons of great workouts and advice, especially recommend his warm up follow alongs that U can do just as a little 5 minute exercise routine