By holding, you can't grow your altcoins but the value will grow so it's already a crossed for me with the method. The best method would be trading and buying through your salary or spare.
These methods will certainly give you additional altcoins and you can grow your altcoins in quantity. But the most interesting thing, what are the altcoins you are going to purchase.
Now that's the hardest part, determining what coins to buy. We don't know which coins will increase in price and which coins will go down in price. Trading is not only a matter of buying and selling but also about strategy and ability to analyze. When we incorrectly analyze it, we will lose our altcoin.