Use legible font
Make your call-to-action button text easy to read.
Choose a font, that is easy to decode in a glance. No research provides a definite answer as to whether serif or sans serif is better. However, the general consensus says that sans serif fonts are easier to read because they are simple and legible even in small sizes.
Don’t let expressiveness affect usefulness. Even though a font looks pretty and will help communicate the mood you want to achieve, it doesn’t mean it is the easiest to read. Pretty doesn’t equal sales – easy to read is more likely to do so.
After reading your copy, users should remember your message or call to action – not the font. Make sure the font you choose complement the text instead of overpowering it.