In the long term, it is best to invest popular coins, because over time they always show profit, but small coins can fall in value over a long period of time, it is better not to invest in them for the long term.
Popular coins are always good to purchase when their prices are low in the exchange due to because when the market starts recovering there are very huge chances for those coins to increase their prices. So always aim for long term investment and it will help you to make a decent profit based on company activity.