Lineage 2 Adena on is very important in the game. There are many mobs that have good drops, but that does not mean you should solely focus all your time on them. However, if you are farming an area with a bunch of mobs and there are some with good drops you would of course choose to hunt those first before the rest.

Avoid buying from NPC merchants. They usually tend to cost more than buying from another player in the game. Taxes there are only 10% and when you buy in large amounts you tend to save a lot more. Do not sell off your loots immediately. Try to find the best barge for them. Private stores can be one of your biggest assets in the game. You can easily browse through a wide selection at various prices, although it may lag a lot but sometimes it can be worth the time spent. You may also want to setup your own store as well when you want to sell off your items. Do not start your store and stare at the screen though, that is just silly and a waste of time.

If you have extra arenas lying around and you tend to travel a bit for whatever reason, you can be traveling merchants. Getting to Giran can take a while and lot of players would rather not travel there to purchase stuff unless necessary. Arrows, healing potions and soul shots are commonly bought items throughout the game. Ideal to stock up a bit on those and setup a store in caves or where ever when you need to go AFK. From time to time if you know the market well enough, there are players who are in desperate need of adena and will sell their item at a much lower price than normal. You can easily buy that and resell later at a higher rate.