DASH is a good coin among many front runner like the Litecoin, Dogecoin and the Monero. So, buy it more now as it is trading in very low price now. You should keep it in your wallet for the long time say 10 years or more. Definitely you get more than millionth of time in value appreciation.
you can prefer other coins rather than dash. dash is good but not best.
you can buy btc in long term. it is best choice.
I didn't even think Dash was too good when the value of dash didn't have outstanding improvement for a long time, a lot of new crypto appeared and started to encroach on the market of dash, dash is just past and outdated, so obvious when it's not talked about too much, long-term investments in dash will not be a good idea. We have a better and more perfect list for that, lots of topics about those lists, some very prominent crypto in the list like BNB, XRP, Bitcoin, ETH, it may be good long-term investments