Here are a few features that make up the best fonts that you should use:
Use well-balanced fonts
Font spacing or kerning
The negative and positive space of good fonts is always balanced. Another point that you should be aware that space should not be affected whether you turn the font into italic or bold. Lato, Karla and Raleway are great examples of a well-spaced fonts.
You can test the legibility of a font by minimising and maximising the size and writing a variety of words with different letters to check whether any letter or word is becoming illegible at a certain size. Nunito, Prompt and Merriweather are all a good examples.
Here are the fonts to avoid in your designs:
Fonts that should be avoided are ones with no balance. Without balance, the thick and thin lines are unevenly distributed, making the letters look weird and all over the place. Slackey is one such example of a font, although it was experimental.