The human eye finds it difficult to read multiple typefaces, so we advise clients to stay with a simple collection of fonts, or a family of fonts. If a design is too busy then this causes confusion in the brain as the eye does not know where to look.
You want your viewer to have a pleasant experience, so where possible keep to the golden rule of no more than two different font families in one design.
The use of fonts should be consistent throughout your branding. There are certain times when a substitute font may have to be used though, such as if there is not a web font available.
The font(s) you choose should reflect your brand. For example, a font that is “fluffy” (such as Brushscript) should not be used for an accountancy practice or a legal firm (unless your name is Saul Goodman 😉 ).