If you have been brewing long enough, then I will just cut to the chase. But for those skimming over this and with a little lack of experience, make sure whatever juice you use tastes good on its own and has no preservatives (common ones are sodium/potassium metabisulphite/sorbate).
In general, Welsch's grape juice tends to ferment out to something pretty crappy so if you are interested in flavor profiles and not just inebriation, then I would suggest starting fresh with any sort of real fruit. Not all grapes are made equal and the best wines tend to be made from the more acidic grapes (those grown in the colder regions of the world). In contrast, commercial industries tend to sell the sweeter grapes with lower acid levels.
For your source, I'd say go for a relatively good juice that is either a non-traditional variety such as apples, pears, peachs, etc. or get a good grape juice that maybe someone else here on the forums could give you some insight into. I haven't personally fermented many grape juices, but I do know a thing or two about country wines. For instance, if you want a pineapple wine, I'd say use about 600 mL of pineapple juice per gallon (depending on your preferrence) which is comparative to a 750 mL wine bottle. I believe that brown sugar pairs very well with pineapple because the sweet, thick molasses flavor goes well with the acidity of the pineapple. Keep in mind, thats my preferrence
Pineapple wine (1 gallon)
600 mL pineapple juice (roughly half a medium pineapple)
1500 grams brown sugar (dark or light and this is approx. 1.7 bags)
or add sugar to your preferrential specific gravity (usually 1.080 is good)
1 gram/liter of anhydrous citric acid (estimated at about a teaspoon)
spring water
Yeast nutrients can be used if you want, but usually not necessary. Keep it around 70 degrees Fahrenheit. For wines, you usually want to get those esters that are often produced at higher temperatures, but if you go too high you can get the nasty odors of fusel alcohols and the such.
I usually use an ale yeast (Saccharomyces cerevisiae) because it is versatile and handles a good alcohol level. Sorry about the long comment. I hope this helped.