Hi! I've got some of the info your looking for!! Here we go-
Homemade fruit mix. I have tried it. My geckos loved it. Passport is the creater and is a member of the forums! This mix lets you add different amounts of the fruits to change the flavors. It is fun to make too!
Home Made Fruit Mix (Frugivorus Gecko Diet)
Repashy products are really nice too. I use the gecko diets and the supplements as well. I buy mine from geckoranch.com . Julie is very awesome to deal with!
The Repashy products I use for my geckos:
Day Gecko MRP-Cherry/Fig flavor
Crested Gecko MRP-Fig
Crested Gecko MRP-Mango
Crested Gecko MRP-Peach
Calcium Plus-This is their calcium/multivitamin all in one supplement
As far as feeding goes, if you only have one gecko over time you'll have to worry about it becoming fat

I would start out with feeding your gecko 2 or 3 times a week on insects and 1 or 2 times a week on either a fruit diet or the prepared diet. Roughly you want to feed an adult gecko 3 times a week minimum. If you can avoid overfeeding you can feed daily too. If you get a baby gecko, feed it daily until about 3 months, then start cutting back to the 3/4 times a week.
Yes you can over supplement. If you go with UV lighting, get a calcium that does not have d3. Repashy has supplements for different living conditions! When you dust your crickets you do not want them to be the color of the dust. You should try to achieve having them about 50% covered. This way you can still see their normal color but they have a slight powdered look. With baby geckos you want to supplement at every feeding. Once they are about 1 year old you can cut back to about 1 time a week on the supplements. If you don't go with Repashy make sure to buy a calcium and a multivitamin supplement.
As far as lighting goes, 12-14 hours a day is great! I would get your enclosure set up completely before you buy the gecko and make sure all your basking areas are at good temperatures and that the overall temperature is correct. If you get this right you will find Phelsuma are pretty easy to keep! I recommend an infrared temp gun of some variety. I use the "Temp Gun" from tempgun.com(got it at a reptile show, love it!) You point, click, and get the temperature from the spot your pointing at. I can check temperatures in 15 different spots in about 20 seconds!! I do not recommend the analog gauges though. I personally have had more than my share of problems from them and believe that they are just a waste of money. There are other temp guns that are probably cheaper too. You could probably go to the auto parts store near your place and pick one up.
Make sure to show us pictures when you finally get your gecko!