I have not gone into the pros and cons of the diamond coin you mention. It’s fair to say small coins can be extremely volatile, and if things work for you, you may make a ton of money. On the other hand, the risk of losing it all is higher.
There are a few alt-coins with extremely good stories, and I am tempted by them, but on the other hand, I feel that bitcoin has the greatest certainty of long term positive return, even if some others look like they will perform better.
Bitcoin is the “Gold” of the crypto world. Some of the other alt-coins are also “precious metals”. Equivalent to silver, platinum or palladium. The majority are not even that. They are like commodities, equivalent to wheat, copper, lead, oil or barley. Some are just equivalent to sand, or sea-water, i.e. of no real value at all.
That about sums it up, with the caveat that I personally have done far better in alts than Bitcoin. You have to choose them carefully, though, and be prepared to sometimes lose.