100 Clicks will give you an idea but the more the merrier for accuracy's sake.
thats a little low even for PPC, if you are on a strict budget then maybe.... but minimum should be at least 1000 (again it would depend on what you were paying per click and what you were getting for a sale), 10pence a click and you get £70 a sale has alot more leway than £20 a sale and £1.20 a click..... just keep improving you're CTR and get a lower price per click...