Level System + HP/MP Limits + Promoting

You gain a level with every 100 exp you gain. Exp is gained by RPing and by participating in events, tournaments, raids and the like.

Your exp will automatically go up, so don't think you need to change anything.

HP:
100xLevel (maximum without special tier: 7,500 | maximum with special tier: 15,000)

SP:
20xLevel (maximum without special tier: 1,500 | maximum with special tier: 3,000)

You can promote to the next tier as soon as you hit level 15, but if you wait until level 25, you'll get more stats. The maximum level of any given tier is 25 unless otherwise stated, so the earlier you promote, the less overall levels you'll gain.