You need sweetener, you need a good cream flavor (Capella's Sweet Cream is excellent), and you probably also need a bit of vanilla in there; TFA's Vanilla Swirl is very good. And 5% probably won't be enough flavoring to even taste, unless you want to steep it for a month; shoot for a combined flavoring percentage around 20% -- banana whatever, cream, vanilla, sweetener. My best original recipe actually is about 30% flavoring -- and I can vape it the minute I mix and shake it, though it's better the next day, and better still in a week. The thing is, to get good flavor right away, you're going to need a fair amount of flavoring, or it's going to take a while for the flavor to emerge.
And definitely don't get discouraged just because you found one brand's flavor wasn't to your liking -- every brand is different, and you might have to kiss a few frogs to find your prince.

Every brand has its strengths and weaknesses, and the only way to find them is to try them.

Andria