You can make so much gold in lotro just by sitting in thorins hall and watching the markets. There are not many people that know how to do this in the correct manner but buying and selling in lotro is the same as any other player driven mmorpg economy.
Start by researching the markets and figuring out what items are always wanted and also sell, It does not matter if they sell for a lot or not, just providing they sell you can make a decent amount of lotro gold just by sellings loads of them. The best time to buy these items is when the trade hall is busy wait untill the weekend when everyone is trying to sell their goods and undercutting one another like crazy.
This is where you will pick up some great deals and then relist them for a better price which in turn you will make a decent profit, you want to sell when it is busy but not when it is super busy!
The earlier you get in and list your items on a weekend morning the more you will make, This may vary from server to server so make sure you take note of what times is best you may even how to test a little bit and this is another reason to start off with cheaper items. I prefer leveling and raid gear to epics since if you make a mistake you do not lose a lot of money trying to get rid of the item.