CHOOSE A PALETTE

In order to to create a kit that is cohesive, most elements and papers should use colors that work well together. You can plan a monochrome color palette or one that is typically associated with special events (like Christmas or Halloween), but you can also use a different palette that simply suits your taste.

You can easily create a whole kit revolving around a palette of 5 or 6 colors.

Even if you choose some colors in your palette, it does not mean that EVERYTHING has to be that color. It means that it should be mainly using them. Occasional use of another color is totally fine.

The easiest way to choose a color palette is to use some already made. Here are some sites you can use:

Cooler
ColorHunt
COLOURLover
Design-Seed
Colrd
Color me curious

You can choose a color palette that attracts you or a palette that speaks to you, but you can also choose a palette that challenges you.

CHOOSE A THEME

Although a theme is not always essential, it is a good to have at least a vague idea of what you will want to use. You can have an event theme like Christmas, Halloween, birthday. You can have a location theme like a city or a country. You can choose an activity like a hobby, a profession, a sport.

However, you can also choose to not have a specific theme, and create a kit that will be useable for a variety of projects. Many designs and elements are totally theme-neutral, so you can also go with that.

It is your call, and neither one is right or wrong.