Your current plan will not work
Dancing several times a week plus overeating will not produce the kind of weight gain you want. It probably won't produce any weight gain at all.
Lift and eat (and dance)
If you want to get bigger, then lift weights, eat lots, and prioritize quality mass gain. Salsa can be part of it, but it can't be all of it.
Specifically, I'd recommend lifting heavy at least twice a week and eating enormously immediately after every dance session and workout. Breakfast and lunch should be substantial too, but be careful of eating too close to workouts or dance sessions.
Foods would ideally include grass-fed & grass-finished beef, pastured pork, farm eggs and chicken, omega-3 rich seafood, vegetables, roots, tubers, greens, as much dairy as you can handle, and good fats like avocado, olive oil, and coconut oil. If you handle it well, rice, corn, quinoa and other grains can add a lot of calories as well.
It would be good to fully understand the depth and complexity of how nutrition affects changes in body fat and body mass. A calorie is not a calorie, and our bodies do not function as calories-in, calories-out machines. This question has some informative answers on the topic.