Unless you have a job that pay large amount of bitcoin, it will take a long time before you can have significant amount of bitcoin that way. Though it really is safe if you just store your bitcoin and never spend it. That is the purpose of savings, slowly build your money. But if you want to make the process faster, save and invest. But there are risk involve if you invest. If you can take the risk, it is a faster way to have a good amount of bitcoin saved.
Well if you have saved enough bitcoins, then its good to invest some of them in trading, as it will give you profits in short time and it will also allow you to grow your coins over a period of time.