Logically , the first rule is "sell high , buy low" . If you want to invest in BTC only then you should only buy and hold for long term , note that It takes long time in order to gain profits in that case.
If you want to get involved with BTC/Alts trading then you could invest in ICOs , most of the time (when It's a serious project) , the price should be x2 or x3 .