Definitely ground if you want a sizeable bush. Lavender is mainly good for the leaves not the flowers, but the flowers make nice decorations. Leaves can be used with anything really, food, drinks, scented oils etc.

RP1

but could be planted in a pot right?

Sure, if you want to keep it more manageable, does tend to grow very quickly.

RP1

Lavendar is also nice planted where you walk and rub against it for s nice smell.

Istanbuljoy

Some people like to use the flowers for decoration, but left uncut they will attract lots of bees and other beneficial insects. The motion of the bees as they latch on to each flowerhead makes the stalks dance.
Ginny