I have been frequenting a great site that I found a little while back called TotallyTortoise.com. There is some pretty good generic information on there that is helpful to any beginner keeper of chelonians. The page that I really like, however, is the Tortoise Blog. This site is pretty well-known so a lot of people get on and ask all sorts of questions. Honestly, many of the questions that I have read would be better posed to a veterinarian than to whomever happens to read and respond to a posting (and that's what I usually tell these folks--"Take your tortoise to a veterinarian").
Yesterday I came across a post from D who has a [beautiful] Golden Greek Tortoise. She asked three very good questions:
1.Is my tortoise getting fed properly?
2.Do I need to trim his nails and how?
3.Is shell flaking normal and should I use calcium supplement again?
Realizing that I haven't addressed the food issue for a while I will answer D's first question in this posting (her other questions I answered on the TotallyTortoise.com blog).
You mentioned that you might try feeding him spinach because some blogs said that it was okay while other listed it as a calcium inhibitor. Firstly, props for trying to research what your Greek Tortoise needs and being willing to do what it takes to take care of him. Secondly, don't give him spinach. The sources that have told me to not feed them spinach have, without exception, been more scholarly than those that deemed spinach to be safe. Here is a link to the best site that I have found so far on what to feed Mediterranean Tortoises (to which group Greek Tortoises belong). You will have to scroll down a bit to see the "Mediterranean Tortoises" section, but you will be pleased to find that it is the most extensive on the page.
Basically, a diet high in weeds and edible flowers is going to offer the variety of foods and nutrients that they both need and desire. Fruits are sparse in their natural habitat and should therefore be offered very sparingly (I don't feed Hector and Phoebe fruit more than once a month or so, and even then it will just be a bite or two) as they often cause diarrhea and can potentially cause more serious health problems. Dandelion greens and edible flowers form a large part of their diet during the winter when it's hard to come by a large variety of other weeds.
Here in the US, Whole Foods has been an excellent shopping location for Hector and Phoebe as they carry a large bundle of Dandelion Green and also small packages of edible flowers for only a few dollars each. We have learned that Hector and Phoebe don't really like rose petals too much (though they will each them a little less grudgingly one petal at a time by hand) but they love snap dragons and pansies. So, we bought some little seed packets, sowed some seeds in a planter, and now we have some sprouts. Hopefully within several weeks we will have something resembling flower buds starting to form (but I'm not a gardener, so we'll see what happens).
Occasionally we will feed Hector and Phoebe some regular lettuce or some tomato or squash. We'll even give them some oatmeal sometimes, but this is always either raw oats or just boiled in water. They never eat oatmeal from a package or with any kind of flavoring or sweetener on it--only raw or cooked in plain water. But we have even strayed away from this because they would not find oats in the wild (but it sure did make Delilah look funny when she ate it).
Well, D, I hope that I have answered your question about whether you're feeding your Greek Tortoise what he needs. Feel free to reply with any additional questions.