I am very new to DIY too, but I have read that the standard is ~20% flavoring?? Now I see its less the 5% most of the time.
Does the percentage of flavoring depend on what flavor company your using?
Better late than never - yes, it depends entirely on the flavours, and on the companies making them. LorAnns seem to be needed in the 20% range, Flavourart in the 1-5% range, and I found professional food flavours where the recommendations given are in the permill range (1-5 gramms per kilogram of food). That's going to need pre-mixes before you can mix it into liquids. Unless of course your test batches are round 100ml.
So you always have to pay attention to the recommendations of the seller, those at least should give you an idea of the amounts you need to work with.
Not sure somebody mentioned that: People said they have a problem with "FA spicy cinnamon candy". I've never seen a "spicy cinnamon candy" on the FA website. I happily vape their cinnamon at 4-5% (which is not very spicy, but tasty), but "spicy c. candy" sounds like a differnt flavour from a different company to me.