There are several methods you can choose from, like:

1. Pick up all the money from the ground. You can do this in bird island. The easiest method is to team up with a high level archer. High level people won't care about money and you can pick them up. It is slow but it is safe and simple.

2. Hunt for meteors. It's easy to do this with your own archer because all players pick up meteors. There are some zones where you can hunt, like:

NewCanyon: low level monsters, big spawn, good meteor drop rate. (Here you can get superior quality items from the ground!)

BirdIsland: medium level monster, enormous spawn, very good meteor drop rate. (Here are lots of low level players that wait to get their power leveled and usually when a monster drops a meteor they will sit on it and you won't be able to pick them up until they move or get killed.)
All high level archers hunt in this zone, so if you don't kill the monsters fast you would better give up!

Meteor zone: medium level monsters.... but very high hp so you have to work a lot to kill them, medium spawn, unbelievable meteor drop rate (200 monsters= at least 10 meteors=1 meteor scroll= 10-15 CPs)
All players from this zone will attack you to get your meteors!
You can't leave this zone. The only way to leave is to get killed at least 1 time by monsters, this if you did not buy CPs from site to get VIP system and get remote warehouse. (if you have remote warehouse you can deposit your meteors and then you can get killed to leave)

3. Become a bounty hunter. It is not very good because you have to kill and detain people to get their gears. If you get from them a good piece of equipment they will pay CPs and get it back. It is not safe at all because they will kill you whenever they see you.

4. Mine Cave: Clear up your inventory and buy a Twin City portal from the NPC named Pharmacist. Enter the Mine Cave to the northwest. When your inventory is filled with ores, right click on the Twin City portal to return to the Twin City, then sell the ores for a profit. (P.S.: Slow but sure. You can also get gems if you dig in the same place for a long time.)

I hope this guide will help you. Good luck!