Every time you cast a spell, you get 3 experience per pip used (0-pip spells are worth 3 experience).
Quests give much bigger rewards. The best experience comes from quests in later worlds, so the fastest way to level up and gain experience is to finish up the main quest series as fast as possible.
The gear you have will quickly become underpowered, and there are quests you will be missing that will give you extra spells. There are a couple of ways to compensate for this without sinking a lot of time.
The first way is to use crowns to buy gear upgrades. This amounts to spending real money, and may not be a good value or a good option for a player.
The second way works well for quite some time. Sell off everything, including snacks and treasure cards, in the bazaar. Use the gold you get to buy upgraded gear. I'd suggest checking the Usable Items Only box, then clicking on top of the cost column to have highest priced gear on the top. Look for gear specific to your school. Within a few minutes, you should have your upgrades. Most gear has a minimum level which ends in a 5 or 0 (30, 35, 40, or so on). Just check back every 10 levels or so.
Also, once you hit level 30, go through Aquila and run the Olympus dungeon once for the wand. You can use this until Darkmoor at level 100.
Completing these quests quickly will require a lot of collecting, defeating several monsters, and defeating bosses. Having a "questing buddy" who knows what they're doing is enormously useful. The boss fights won't have any extra enemies, and the collect and defeat quests will go far faster. If you need to run and learn a spell or visit the bazaar, porting back to them when done will also save you tons of time.
Questing on the story-line quest is the best way to level up. I only stray off of story-line quests if I need to be a higher level to enter a new world but in your case since you are a new player, take side quests if you are having a difficulty questing in the main quests. Extra levels in a world can really be useful.
Story line quests in the long run will always be more efficient. If you finish you current world and move to the next world as soon as possible, you will enter a new world with a higher tier of average xp-reward. If you do side quests, you will remain in a world that gives lower xp compared to a world you could already be questing in that offers greater xp/quest on average. Investing into aoe (area of effect/all enemy hits) treasure cards can also greatly enhance your questing speed. Purchasing athames and rings that gives increased power pip percentage once around level 25+ also speeds up questing.
At level 30, Cyrus Drake will invite you to his school to get you to go to a place called Mount Olympus. This dungeon has a boss that drops a staff called "Sky Iron hasta" which gives +10% universal damage and +1 power pip at the start of a fight. I'd highly suggest doing one run of this dungeon for this staff as it is 100% drop rate from the second land boss.
