If you invest in alts now, it is better to choose those that are at least in the top 100 market, because not all coins can be reliable anymore
Top 100 contains some bad projects, IMO. Therefore, I would like to narrow down my observed coins for my investments into top 30 or 50 only. Among them, it is safer to invest in old altcoins, rather than new ones - that have less than 2 year of history