It depends on what you’re trying to do.
I am a soapmaker by trade, and for my own use, I also make lotions and balms and such.
As a matter of course, I look at items on-shelf to see what is on-trend. Oftentimes (especially with the “all natural” craze going around, store-bought products are made with the same ingredients I use in my cottage products.
The issue is usually one of preparation and proportion. Sure, you can read on a label that the facial scrub you like is made with X oils and Y essential oils and Z other ingredients, but do you know how it was prepared, how much of which to use, and what a safe usage rate is?
You can often Google for DIY recipes, but those are often made up wholesale by “Mommy Bloggers” who are mostly guessing, and those recipes can often be dangerous when used over time. I saw one today, for instance, for a lotion bar that included lemon verbena essential oil. That oil is phototoxic – If you put it on in the morning then expose your skin to sunlight it will literally burn you.
So, y’know. Be careful.