You should learn the both and eventually makes your choice, no crypto enthusiast should limit himself to only a particular aspect, you need some trading knowledge in making investment decisions, both type of trading all have different outcome and requirements. Particularly for a very busy person, long trading should be the best as you do not habw to watch the market all day while short trading requires constant monitoring
Even tho I do daily trades time to time I still love long term investments. I do buy some smaller coins that I think is on the verge of exploding and if it doesn't do that in couple days I sell it and cash back to bitcoin however on coins like nano and specter I just invest into them full on because I believe they could be more than what they are right now.
Nano maxed out at 34 dollars and right now it is fraction of that, specter is the same it was once over 6 dollars and right now its at around 20 cents levels, these coins do worth at least half of their all time high prices so I see a big upside in both of them.