Simple mistakes to avoid:

  • Don't cast Lesser Poison on group raids. There are a limited amount of spells the group can apply, and there are much better spells.
  • Don't spend your early stat points on attack or defense. Put them all into Energy and Stamina until LSI reaches 7. Or, if you want to build a PvP character, then using a base amount of stamina and negligible energy is recommended to keep your level low (since Duel is based on BSI).
  • Think twice (or more) about spending your Planet Coins on initial gear, armament, troop or general in the bazaar; it becomes virtually worthless in a few days. Expeditions(but mostly not even for flash sale), legion and premiums are a much better investment. A Good Legion at 10 planet coins like Thornvenom Stride will last you forever whereas equipment such as the Gladiator's Set will last you a week or so. If in doubt about whether or not to use your coins, then you can always seek advice on the forums, your guild or in chat.
  • Don't forget to equip and update gear in both modes of PvP (you need to do it again for Duel and again for Colosseum).
  • Do NOT buy gold or army size with planet coins, they are the biggest rip-offs ever.
  • Do not place a Rallying Cry for the same raid several times in chat. It rarely helps to complete your raid, and can make other users mute you. You can however post it to multiple rooms and the forums.
  • Do not tag a DL raid (Dragon's Lair). Join only if you can fulfill damage requirements. FS on Normal - 7.7m, For Hard - 38.5m, Legendary - 77m and Nightmare -  115.4m.  Unless you can do 50 million points worth of damage comfortably, you won't get anything useful at all, and you are taking up space that heavy hitters could use, thereby also reducing the chance the raid will finish in the first place.
  • Do NOT tag ANY raids unless you can fulfill damage requirements (generally the same reason you shouldn't tag Dragon's Lairs).
  • Do not cast Quicken Mind on tiered raids. Using damage magic means you can hit more of the same raid in one level.