Brush: The most useful tool in my opinion, it's to add effects, splashes, etc. you can download brushes. we can download at Free Photoshop Brushes at Brusheezy!
Font: Type of letter, we can download new fonts, at dafont.com
Size of a signature (pixels per pixels):
This can vary depending on what kind of sig we are looking to make
normally the sizes are from 125 of height to 250 and 200 to 400 of width.