You are right, with the number of coins and tokens in the market right now, deciding on the type of coin to buy or discovering a coin with great potentials can be a herculean task. However, I think that before embarking on such you need to first decide the type of investment plan you want, that is, is it long term or short term, after deciding on this, it will go a long way in helping you sort out projects.
Now, if it's for long term, then top 100-150 on coinmarketcap can be a good place to get started, these are coins which have tried their best to reach that rank on coinmarketcap and as such will only keep trying to maintain growth.
On the other hand, if it's for short term, then check upcoming projects and their team motive towards the platform, in addition to this should also be the use case of the project, once everything is in place, check the exchange they are listing on before making your final move. Since it's for short term, know when to take profit.