Guide to Flavouring Percentage

This will give you a starting point for TFA (The Flavor Apprentice) flavorings:

Please note that these are just some suggestions and percentages that worked for users of these flavours. The percentages below are for single flavour mixes.

Absinthe: 10%
Almond Amaretto: 5-10%, 5/5
Red Apple: 10-15%, 4.5/5
Apple Pie: 10-12%
Banana Cream 10%-15%
Banana Nut Bread: 5-7% (Great for mixing)
Bavarian Cream 5%-15%
Bittersweet (Choc): 10-15%, 
Black Cherry: 5-15%,
Black Honey Tobacco: 3-5%
Blackberry: 6%
Blueberry: 15%
Blueberry Extra: 10-13%
Brandy: 5%
Brown Sugar 15-20%
Bubblegum: 10%>
Butterscotch: 12%
Caramel: 10-15%
Caramel Candy: 15-20%
Caramel Cappuccino: 1 drop in 10ml base 
Chai Tea: 10% Very Unique, a must try
Cheesecake: 5-15%
Cherry Blossom; 15%
Caramel Cappuchino 1 drop/10ml
Chocolate: 10-15%
Chocolate Mint: 10% (more chocolate than mint)
Cinnamon Red Hots: 5-10%, 5/5
Cinnamon Spice: 1% is noticable 5% is strong
Coconut Candy: 10%
Coconut Extra: ~10%
Cola Syrup Flavor: ~8%
Cotton Candy: 10-20%
County Fair Cotton Candy: 5-10%
DK Tab 555: 3%-5%
Dragon Fruit: 5-12% (better mixed with another fruit)
Double Chocolate (Clear) 10-12% 4/5
Double Ry4: 5%
Dulce de Leche: - overpowering at 20% - good for combining
Earl Grey Tea: 5%
French Vanilla: 5 - 10% 
Graham Cracker: 10-15%
Grape: 12%
Green Apple: 12%
Gummy Bears: 8-10%
Hazelnut Praline: 5%, 2/5
Honey: 10%
Honeysuckle: 10- 15% - very good but FYI will crack a tank
Horchata: 5%
Irish Cream: 10 - 12%
Jamaican Rum: 12%
Juicy fruit: 13-15%
Juicy Peach 17%
Key Lime Pie 12%
Kahlua and Cream: 10%
Kona Coffee: 1drop/10ml
Kiwi Double: 5%
Licorice:10% needs a few weeks to steep
Lime (oil-based): 1-5%
Lychee: 5-7%
M-type Tobacco- 1% for starters It requires a loooong steep!
Malted Milk: 5% (best mixed with other others)
Mango: 13%
Maple: 10%
Marachino Cherry: 5%, 4/5
Maraschino Cherry Second opinion: 1% 
Marshmallow 5% for a good addition, 10% for a main flavor
Milk Chocolate: 20%
Mint Candy: 12%
Molasses: 2-3% (best mixed with others)
Mt. Dew 10%-20%
Orange Cream: 5-10%
Papaya: 10% 5-5 (Very Fragrant)
Peach (not juicy) 12-15%
Peanut Butter: 10-15%
Pear: 10-15%
Peppermint: 15%
Pie Crust: 3% for mixing (gets kinda acidic above 5% IMO)
Pineapple: 15% 4.5/5 ( authentic flavor, I used 5% EM to sweeten)
Pizza: ~5%
Plum: 5-10%
Pomegranate: 7.5%-14%
Popcorn: 13%-15%
Pumpkin: 7%
Raisin: 1-3% (Powerful)
Raspberry: 10%
Red Bull: 10%
Ripe Banana: less than 5% (very strong and known to crack tanks)
Red Oak: 2-3%
RY4 Double- 15%
RY4 Asian: 10-15%
Smooth 2 drops per 5 ml
Spearmint:
Strawberry: 3%-15%
Strawberry (Ripe): 10%
Strawberries & Cream: 10-12% (good on its own, better with 3-5% EM)
Sweet Cream: 5-10%, 4/5 - This flavor recommended for combining with others.
Sweet Tart: 10%, 5/5 - Tastes more like Smarties add sour
Tangerine (oil-based): 1-5%, 5/5
Tiramisu-- 1%-5% Over 10% tastes like burned coffee
Tobacco Blend Alcohol: 2.5%
Toasted Marshmallow: 10-15%
Toasted Almond: 15%
Tutti Frutti: 10-15%
Vanilla Bean Ice Cream: 4-8% (excellent mixer)
Vanilla Bourbon: 10-15%
Vanilla Cupcake: 20%
Vanilla Swirl: 10%
Vanallin: 10%
Violet Candy: 10 - 12% (one of our favorites)
Waffle: 20%
Watermelon: 15% 
Whiskey: 5%-10%
White Chocolate: 10% 
Wintergreen: 10-15%
Sweetener: 2%+
Sweet Tarts 10%
Cinnamon Red Hots 3%
Holiday Spice 3%
Key Lime 7%
Bavarian Cream 5%

Source: www.planetoftheapes.co.uk