There's a reason #neverskiplegday is a thing on social media; lots of people do. It's one of those gym sessions most people would happily swap for back day, chest day, arms, or in fact any other upper body day you can think of. Why? Because leg day is tough.
With the right training and nutrition, it is often said that the average man can gain around 1-2lbs of muscle per month and the average woman around 1lb. Ignore the 'quick fixes', it's patience you need to exercise