How do you do your own research if the coin is a good investment?
For me, I always look on the purpose of the project, the team behind it, what exchanges is it available on etc. And one of the important thing for me is the total supply of the coin.
I also research if the coin is Proof of Work (POW), Proof of Stake (POS), Pre-mined or other.
Before buying a coin, one must read its whitepaper and see for what use the coin is being created for, does it have any real world applications, which team is working behind it, are they being transparent, how many partnerships they have been able to make so far, on what platform the coin is being created, what are the key features of the coin, what are they doing to promote their coin and gain people interest, what is the supply of the coin and many other key features. Reading its white paper will provide quite much info and you can judge whether it seems legit or scam.