This "strategy" of yours will completely depend on if you can actually pick the right coins to buy; which is like 90% of the challenge. It might sound easy on the surface, but it's definitely going to be a lot harder than it seems.
If it went down, I still wait until it will go back up +10%. It's ok if it will take weeks.
Waiting weeks won't even be your problem as a lot of existing coins don't even go back up in price after crashing.