Best tools and equipment to digitise film negatives with DSLR, without breaking the bank

I am considering buying Lomography DigitaLIZA film masks for both 35mm and 120mm film to use within my digitisation process, however I am unsure of the best methods around the other areas of my process.

I struggle for back-lighting of the negatives mainly. I have an iPad in which I initially used, showing a blank white screen with my film negative on top and a glass/perspex sheet on top to flatten out. However, I found that upon inspecting the photos of my negatives, I could actually see the pixels of the Retina display in the whiter areas. I have gotten better results with no pixels in the background when lifting the negatives up, away from the screen and resting the setup on top of say a cardboard box, however this can sometimes lead into another problem… Making sure everything is level.

I have seen people use copy stands and film viewing light panels, but from what the products I have viewed this can start to incur great cost.

Does anybody have similar experience with digitising film negatives and a way to do it without breaking the bank?