Sarsons ready spiced Pickling Vinegar is good and adds all the spices for you. But this is a good recipe
For every 2kg beetroot
1 ½ litres vinegar -malt vinegar or wine vinegar
1 tablespoon coriander seeds
1 tablespoon black pepper corms
5 cloves
I cinnamon stick
2 bay leaf
50-100g Sugar I dont add the sugar but my aunt did.
Its really about what you like and trial and error.

many thanks for your fedback