You can create multiple designs using polka dots. You don't necessarily need any tools for that, it can be very easily created with toothpicks.
You could create beautiful ombre nail art with a makeup sponge. Those are very easily available and then you could get creative with the colors.
Paint 2 or even 3 colors in geometrical figures with the help of tape. Just make sure that each coat dries completely before using the tape, else the paint would peel off.
Use glitters when the paint is wet and you can make your nails ready for a party.
Splash or splatter nail art can be done using only a straw. Just dip the straw and blow it on your nails. A white nail paint with splashes of 2–3 colors looks beautiful with very fewer effort.
Just adding rhinestones to plain nails is not only quick but looks chic too.
And the most basic and classic French nail art could be done anytime with only one color… white.