You'll need adhesives to assemble certain printables, like attaching cupcake toppers to paper straws. A printable designer's go-to adhesive is usually a hot glue gun. They're inexpensive, and the glue is guaranteed to keep everything in place. You can also use glue dots, double sided tape (permanent is preferred), glue sticks, or regular tape.
If you'd like to create hand-lettered printables, consider taking a custom lettering class so you can edit your designs in Illustrator. Hand lettering is an excellent way to make a printable truly custom.