You only want to upgrade your Hongmoon Weapon, which you’ll get from your class quest in Bamboo Village. This weapon can be upgraded up to Level 45. The same is true for your Hongmoon Amulette, Ring and Earring, which you will also get from your class quest.
When you are at Croaker Lagoon (North of Jadestone Village, around Level 16 or 17), kill Ploggle King Giganura a few times. Using a few spare keys (but not all), open his loot boxes until you have a Ruby with 50-60 Additional Damage on Attack, and an Amethyst with 30-50 Life Leech or 30-50 Instant HP Recovery on Crit. They will help you greatly up to level 45.
Keep your Soul Shield up to date, but only replace parts if the stats are better. You will get the first set from the Wheel at Foshi Pyres (level 8). This set can be replaced at level 20, either with the Viridian Stone Soul Shield, bought with Viridian Stones from the Merchant in Jadestone Village (more HP), or with the Heroic Set dropped in Blackram Narrows (more Block and slightly more Crit at Blade-Soul ). The next upgrade should be at level 28 with a choice of a Cinderlands Set, bought with Cinderlands Valor Stones in Yehara’s Mirage, or the Golden Deva Set from the wheel at Crescent Spring.
Here’s a great guide for which soul shields to use at which levels if you’re more interested.
More tips from /u/Terrormeep , link to comment:
Once you get to Jadestone do all of the profession gathering quests. They’re extremely easy to do and give a whopping 1000 exp each, which lets you skip more time-consuming quests early on (such as the first hub in Cinderlands).
Once you get your desired professions, try to make as many crafting orders as you can reasonably afford. It’s low-maintenance and saves you some time endgame as there’s no way of decreasing the time required to level it.
You can use macros to work around the mouse input delay and rebind the ss evade to a single key.
From /u/Brysonds , link to comment:
One very important one to add is that doing achievements increase character stats. For instance, doing Blackram dungeon 10 times gives your character 400 HP.
Another is once you are level 15+ winning ten 1v1 PvP arena matches gives you 70 defense.
He’s working on a list atm. I’d like to add though that from what I remember you can only choose one of these stats increases, you can choose which one from the Achievements tab.