If you're looking to be frugal over the long-term I really wouldn't suggest buying things at Dollar tree, You get less for your money per ounce then if you bought a whole container of it from somewhere else. It's kind of like the concept between Walmart and Sam's club. The more you buy it one time the cheaper it is per ounce/pound.
Like buying peanut butter at a normal supermarket is cheaper by ounce then buying these little containers like this.
But I do understand if you don't have the ability to buy in bulk/larger quantities and you are paycheck to paycheck then this is a viable alternative even though you are spending more money in the long term.
I understand if at the end of the month you only have $25 and you need groceries well you can't just wait until next paycheck and have $50 and get bulk groceries because in the meantime you don't have food.