Basic crochet stitches such as single or double crochet are a must and you can surely create many projects using only a few. However if you want to create some unique items, you should learn how to add texture and elevate your crochet pieces to another level.
A great way to learn new crochet stitches is to make dishcloths and coasters. These square or rectangle projects are fast to crochet and can also make a great gift for many occasions.
There are many crochet stitches that will be suitable for Blankets and Throws. You want them to be pretty solid to keep you warm. However, if you are planning on a decorative bedspread, go for more lacy patterns.
Tops and Cardigans also call for decorative stitches so learn as many as you can not to miss on exciting patterns.