One of the mistakes that many new Castleville Legends players make, is assuming that they don't have anything of value to contribute to the Sea Trading marketplace. Nothing could be further from the truth! The sea trading ships are an incredible boon to any player who uses them correctly, which is why I encourage you to begin using them - extensively - as soon as they are available to you at Level 5.
The reality is that there are many, many high-level players who will pick up all sorts of very basic items in the market, just to save themselves time or production hassle. For example, their workshops are all busy crafting items with crafting times of an hour or more, but they need plain torches or ladders for an exploration. If these things are available in the market, they'll be snapped up in a heartbeat!
Same goes for your other workshops. Basic items like cheese from your dairy barn, plain gloves from your tailor, and cheese omelets and apple oatmeal from your trail kitchen, will all be eagerly welcomed in the market.
So if you want to maximize the amount of money you make at the lower levels, make sure you never let your buildings sit idle while you're playing. Always have them producing something - preferably in quantity - so that when your ship comes back you can load it up and let it earn for you. Remember that every item page on this site has a guide to tell you how many of an item will fit in a single one of your ship's slots, so you can produce away, and know just exactly how many of each item you'll be able to ship when your boat returns.
Even if your workshops are all busy, generating some extra eggs, milk, wool, carrots...whatever you can...can earn you coin, although admittedly not as much as finished products will. Once you get a blueberry patch, this is a great one, as blueberries sell at a decent price, aren't used in many low level quests, and are always in demand because of their long growing time.