I don't know about the others, but every time I go on a trip I feel the need to bring home some of the local products, something to remind me through taste or smell the emotions of the holiday. And there are always the small gifts for the loved ones.
The first advice I'd give you would be to try the local products before leaving the island. I don't know how, but once you take them home they seem to lose some of the taste and savor they had in their local environment. It could be that they associate to the beauty of the landscape and to the relaxation you feel during a holiday.
The Papanikolau dairy products
The small Papanikolau dairy factory is in the Makrilies village and it only uses the milk of the island provenience. You can buy here various types of local cheese (provio, makrilisio, mizithra, xirotiri, kascavali, graviera) which later maybe you can use for a cheese tasting paired with wine or beer.
The olive oil
The Samothrace olive oil is a "must take home" product. Ok, I know that you can find olive oil in every supermarket, but it really isn't the same thing.
Samothrace has a long olive oil tradition, and the olive groves cover wide areas in the western and southern parts of the island. The olive oil is pure, light green colored and very flavored.
You can often buy it from the owner of the villa where you are accommodated or in the neighborhood. You can also buy it from the Papanikolau factory. The price for a 5 liter tin is around 35-40 Euro.
A special note deserves Astrae, a family business run by a biologist and an environmentalist. Their olives and oil won many prizes, go to export and you can find them in the shops of Chora and Kamariotissa.
Samothrace is an island rich in wild flora and not yet polluted, so the honey here is pure and of high quality. Very special is the oregano or thyme honey – you can find it in Therma, but there are a lot of hives on the island and it would be better to buy it directly from the beekeepers.
Marmalade and "spoon" fruits
The traditional sweet of Samothrace is called praousti koutaliou, which means that yellow-orange local fruit (praousti), preserved in sugar syrup and than enjoyed by spoon (koutali), usually next to the Greek coffee. Other spoon sweets are cherries, walnuts, figs or apricots.
The marmalade could also be a nice present. You should try the homemade pumpkin, grape or sour cherry marmalade from the O Vrachos Taverna in Profitis Ilias. The price for a 500g jar is about 10 Euro.
The people of Samothrace are proud of the high quality oregano.
The wines from Melmar Winery
Plan a visit to the only winery of the island (you'll find it in Dafnes), find out its story from the enologist and taste the wines while you enjoy the view of the sea! Before leaving you can buy the wine bottle (or bottles) that you preferred. The prices vary between 6.5 and 12 Euro.
The Fonias Pale Ale beer
Samothrace does not only have a winery, but also a craft brewery. It is owned by an Athenian who fell in love with the island. Samothrace Microbrewery is on the road from Kamariotissa to Chora and it's open between 10.30 and 13.30. Here you can buy the beer directly from the source, for 2.2 Euro a bottle of 330 ml.
If you'd like to feel a local for some moments, have a seat at a taverna, order a tsipouro (spirit) glass and a plate of meze (appetizers) and take your time to enjoy life. If you want to take it home you'd better find a local producer.
Tip: ask the owner of the taverna – most of the times their tsipouro is homemade.
Besides the milk goat or olive oil soaps, the small producers of the island (like Geophoria or Armonia) create plant tinctures, essential oils or face creams out of plants. You can find this kind of products in the various shops of Chora and Kamariotissa at Trapeza Cafe or at Papanikolau shop in Makrilies.
There are several souvenir shops in Chora or Kamariotissa. The most memorable one is the Goat Shop, where everything is plastered with goats.
As on other Greek islands, the local producers created cooperatives, in order to better market and sell their products. Two women cooperatives, one in Kamariotissa and the other one in Paleopoli offer marmalade, homemade pasta, aromatic plants, soaps, liquors, tsipouro or honey. The olive oil producers also have a cooperative.