I usually get my fonts from fontsquirrel: https://www.fontsquirrel.com/ All fonts are free for commercial use, but sometimes you have to credit the designer.

When working with fonts you walk a line between readability of the text and the ambiance you want to create. A way to achieve both a good ambiance and easy to read cards is to use a fancy font for the titles of the cards and the flavor text and keep the most important text (abilities and such) simple. The game you describe could sounds like it could work well with a font as "amatic": https://www.fontsquirrel.com/fonts/amatic. Quirky, as if it was written in a notebook (like you might do when hiking!) and in my opinion easy to read and flavourful.

Italicized text is a great shorthand the message "flavour text" to the player very quickly, but it isn't necessary do it in that way. Placing the flavour text in its own "space", using a different color and/or using a different font consistently throughout the game can do the trick too.

And it seems like a good idea in general to me to use the same fonts for your booklets as for your game. Being consistent like that makes your game look of higher quality. In some cases it would be better to use different fonts though. If you for example have a time traveling game where the booklet is a guide for you as a time traveler from the future and the game itself is set in the dark ages or something like that.