More isn't always merrier ... at least not when it comes to DIY.
Is like chili ... too much of it , you taste only hot and won't be able to tell whether you're chewing a fine steak or a soggy dishrag cuz the 'hot' overpowers everything else.
Start low , even tad below what the respective flavour maker recommends. Adding flavour to taste is easier than trying to salvage a batch that got overdone ( ever tried un-salting a soup ?

)
Steeping, aging, whatever you call it ... means giving your mix time to homogenize and develop.
Flavours I'm using are highly concentrated ( making them more cost-effective in the long run ), highest I ever used was 7%, some tobacco flavours go fine at a measly 2% ... And that flavour needs to 'populate' the remaining 90 plus per cent evenly throughout your mix.
Means you either give it time ( a few days for fruity flavours till several weeks for tobacco flavours - anything cake-ish or cooky-ish is somewhen in between ), or you speed up the process actively: There's a ton of threads, utilizing anything from magetic stirrers to ultrasound cleaners and what have you. Know of a guy who filched his lady's vibrator to give his juices a good rattle

...
I've got a crosstrainer ... Taping the bottles to one of the pedals gives me and the juices a good workout...
So don't chuck that starter kit just yet, please...
Start low, let sit, taste, add, let sit,
once you get the ball rolling it'll be fun once you vape your first good ones while mixing more for later ..
