Level 25 Crowns gear is sold at the various shops in Marleybone. There is also an excellent Crowns wand/sword, the Phosphorescent Maul, which grants a power pip at the start of battle.
The "best" equipment is a matter of what you want. Some people want as much health and mana as they can get; others want as much power, accuracy, power pip percentage, etc. as they can get.
The best way to find out what works for you among non-Crowns items is to go to the Bazaar, check "Usable", and sort by highest level (this takes two clicks), then school. That will show you the strongest items specific to your school. You can then decide what suits you best.
Note that with rings and athames, the best item for you is often NOT school-specific.
