By creating a plan, you will less easily become overwhelmed or influenced by the products you see.
Take a look at your overall non-negotiable expenses (i.e. rent, utilities and any bills) and see what is left over and work within those boundaries.
Take a few moments to comparison shop. There may be an opportunity to purchase the item for a better price.
Whether it is cash or debit card, either will help you shop within the means that are within your bank account.