I usually by the house brand of anything the first time I buy anything. Cooking ingredients, household chemicals, drugs, tools, and anything else you can think of. I have found a number of places where saving money is not worth it, the difference between organic tomatoes and the conventional ones is huge for example but if you don't care about tomatoes you may be fine with the cheap ones.
There are a few things I will spend good money on first time through. Basically anything I am not going to have a chance to replace if I don't like it. I had to replace the floors in a few rooms in my house. When we first moved in and could not afford nice carpet. It took 10 years to wear out the carpet and for us to have enough to replace it. If I had to do it again I would have stuck with the original longer to save a bit more and put in better flooring.