Cheapest demijohns I have found were left next to a glass recycling area. You need to sterilise them anyway. Next cheapest was from the local tip/transfer site. Then the small adds. Check the hole in the neck size as there are two sizes and the bungs are only the large size. Said before, but I used to go to the fruit market as it finished and pick up kilos of lovely fruit. Don't forget that you can brew with mixtures of fruits and mixtures of vegetables or mixtures of both. You need to think about body, available sugar, pectin haze and yeast nutrients.