When I make a white mix, I use the amounts of oil and water specified on the box. You can add an extra egg or egg white if that's what it calls for. I also throw in some sc. I don't usually measure it but I believe it ends up being between 1/2 and 3/4 of a cup. It turns out great.
Use a "tried and true" recipe found on this site - they are broken out by scratch or mix (use the "stars" to find a good one that you would like to do). Next step (for future reference) would be to research special flavorings and emulsion. Check out Earlenes site for Butavan for instance. Many a post has talked about them here on CC (ex. Wedding Bouquet also known as Creme Bouquet). Let me know if you need to know some sites to buy them.
Tip: Use Canola oil if you arent already. Later you can experiment with other light tasting oils...just fyi.
The *original* WASC cake recipe that I came up with is perfect to your request.
It is posted in the recipe section and in many forum posts. Since I myself have trouble finding it using the search function I'll post it again for you here.
The *original* WASC cake recipe by kakeladi
1 box white cake mix*
1 cup flour
1 cup granulatged sugar
generous dash salt
3 whole eggs
1 cup sour cream
1 cup water*
1 Tablespoon almond extract*
In a bowl, mix together dry ingredients; using a wisk is helpful.
In bowl of KitchenAid mixer, place all 'wet' ingredients. Add about 1/2 the dry mix; stir on #1 for 30 secon ds to moisten; add remaining ingred and again mix on #1 for 30 sec; beat on #4 for 2 minutes. Pour into prepared pans and bake as any other cake you make.
*NOTES: Any cake flavor can be used. I prefere Betty Crocker. Match the flav oring to the cake flavor....ie: lemon extract w/lemon cake etc.
A combination of vanilla, butter, and almond extracts is excellent for almost all flavors. Some people do not like almond/are allergic to nuts so they use all vanilla flavoring.
This make an amount of batter = to 1& 1/2 mixes - enough to fill a 9x13; a 12" round; 10" sq; two 8" rounds; and/or other pan sizes/combinations.
sugaah - you are in luck b/c kakeladi's WASC recipe would have to be one the anchors to this site IMO. 
Wedding Bouquet and Creme Bouquet are actually not the same thing. They are two separate flavorings. Wedding bouquet has a more almond scent while Creme Bouquet smells somewhat citrusy. Opinions are divided on which is better.
oh my goodness, I bought Wedding Bouquet from Kitchen Kraft and they sent me Creme Bouquet so I assumed it was the same. Ha Ha Ha! I use Butavan for that "almost almondy" flavor. Back to online ordering - thanks for clearing that up - how silly of me....but more experimenting - yeah!! 
Quote by @%username% on %date%
%body%