Just set aside 500 dollars a month and when you have 5k you just wait till bitcoin drops down and buy 1 with that 1 bitcoin you invest in other coins and make the most out of them that is what i did and i have a lot of profit out of them.
In my opinion that is not a valid strategy anymore, that will take to you 10 months and ten months is an eternity in the world of crypto, just look where the price of bitcoin was 10 months ago, so the only strategy that we can apply is to invest every single dollar we can afford in bitcoin as fast as possible if you do not do that you are going to lose a great deal of profits.