You need to build a portfolio of flavours to experiment with, but for starters I'd go for something like this, to which you can add any fruit flavours you like:
2% Any custard
2% TFA Bavarian Cream
2% TFA Sweet Cream
0.5 % Capella Golden Butter
0.5% FA Condensed Milk
will give this one a go. ta muchly.It doesn't get much simpler than "Mustard Milk" to introduce people into DIY. 2 ingredients and shows you can easily make your own juice better than all the sweetened premium stuff.
6% TPA Strawberry (link)
8% TPA Vanilla bean ice cream (link)
Both of these can be bought at www.chefsflavours.co.uk and you'll need some 72mg nicotine if you're making your own. I can't post a link on here but if anyone wants it just pm me.
Edit: links to flavours on Chefs