Do premium plugins & photos affect sales for new sellers?

I see that HTML templates that sell well include premium plugins like Revolution Slider. The photo used for the presentation template is also good & when I tried to find it on a free photo site it didn’t even exist. Is it really a guarantee that premium plugins can increase sales? Then what about photos, are free photos from there still lacking in order to increase sales?

What made it hard was that when I was just starting out, I didn’t have enough capital to buy premium plugins, subscribe to stock photos.

Thank you