Eventually you're going to reach a place on your writing journey where someone is going to request an autograph of your book. That's a feel-good moment as you can imagine. There are several ways to set up shop and sell your books at the market square with pen in hand, which brings me to the gist of this entry. From my personal experience, and comments in general from other authors, the INC. R-2 Rollerball 0.7mm pen in black ink is 5-star perfect and inexpensive.
Also, it's a lot quicker to type a standard greeting to affix to the inside cover of your book if it's a personal gift. I like to type mine up in PowerPoint which allows for borders, etc. I then print it out, cut it to size, and recommend using a simple glue spray or stick to affix. After that, get your pen, practice a few sigs, and then sign away. It feels good and a perfect way to personalize a gift.