Avoid new coins if you wanna trade in the long term. Although listed on the top exchanges, it isn't uncommon for them to actively engage in fraud in terms of price manipulation and trading volume.
You can have general mentality of not investing into altcoins because all of them are good for a short term profits but not long term, still there will be people who are taking that chance with startups on IPOs and get fooled by IEOs here which are named to imitate but failed to deliver. If you want to keep your coins safe, buying bitcoin is what I suggest people.
Long-term investments must be made on top altcoins
Even top altcoins are not give market performers. The only coin you need to make a good profit from is bitcoin - this has been proven so may times seeing the bear-bull cycles and watching the bitcoin and altcoin markets separately.
For a good capital, putting >90% into bitcoin for the amount allotted to cryptocurrencies is a very wise decision.