This is a bit late but....
The market in Rose is pretty messed up, but you can still farm for items that can sell for a decent amount in-game. My suggestion would be to reach max level first, then do dungeons like Cave of Ulverick and Sikuku Catacombs.
In SC, you can get exalted items that sell for 100m each(roughly), Seperation drillls that sell for ~500m and 9th grade binds etc that also sell for ~5m each. I wouldn't do this unless you have exalted gear already on your chars as it is a bit harder than cou.
You can also get unique max stats from CoU (price varies depending on the stat), elements (again, price varies depending on which element) , and lisent U's mainly (selling for ~15m each currently). If you get 999 U's that's 15B already, and with the right classes (aoe/fs/etc) and the drop rate items (gems/costume) its pretty quick. It just takes time to gear your char to do strong aoes so you can spam quickly. It would help to join a clan that has drop rate passives and where people are willing to do these dgs with you (there are many). Note: you can single queue in cou and join, but 9.9/10 people will just rush and kill the bosses only, so its best to find a group to clear all the mobs in dgs if your farming lisent u's.
Outside of dgs you can also farm bosses like mastyx etc for medallions (prehistoric mastyx medallion sells for 10-12B at the moment), gems, level 240 accessories from wandering bosses in orlo, and a few more items. But keep in mind it will be slow and painful especially at the start since you wont have drop rate items that will boost your chances of getting good drops. (so like honeybunz said, watch for exp/drop events).
Also, as you do dungeons you can gain valor that can be used to buy items from the valor shop. You can use those to increase your gear or buy items and resell them to players for decent zulie. (although i suggest you invest in you char using those points).
Good Luck XP