Welcome, @jolien!
Francisco shared some great simple spell jars. There are many spell jars on Spells8 to choose from- and know that it is possible to make substitutions or go without ingredients to suit the materials you have on hand!
Take a look at Substitutions in Spells and Rituals for some advice on switching ingredients.
You can also try designing your own spell jar using the step-by-step guide in How to Create Your Own Spells 
Wishing you the best of luck as you make your spell jar. Blessed be! 