Put broken pots, broken up polystyrene packaging, rubble, stones, bits of slab etc. in the bottom for drainage (and to fill it up a bit) and mix topsoil, well-rotted horse manure and compost and maybe some play sand to fill it, and some proper home made compost if anyone will give you some. :) Bought compost on it's own is too light and unifom for veg, all the water runs straight through and the roots have little to hold onto