Point number one is quite hard to tell I always fall on this one, maybe I'm not doing my assignment because you never know after purchase if it is still going to go down further, even if the price stop falling for a week, there is still no guaranty that it will not fall again, it's still a gamble for me.
I would like to tell you my experience to explain your concern:
1. Before buying a certain crypto symbol, you should spend time to read and evaluate the project as carefully as possible. I mean here the Fundamental Analysis and update news about it everyday. As a consequence, you can find yourself its real value. So, when it fall again, you will NOT, at least in panic sell mood. Moreover, you should learn about Technical analysis to find out the support areas as well.
2. Please don't consider crypto trading is a gamble, it's just a game only. We are just game players and try to control our feelings before thinking of having anything