I'm going to go against the grain and suggest that you ignore all of the above advice,
especially since you are playing a caster class. In EverQuest plat doesn't really help you level (unless you have enough to buy something like a Fungal Tunic), but leveling helps you earn
a lot more plat.
In other words you can choose from spending time getting plat now (when you can earn maybe 10 plat an hour, not counting the time you spend selling in EC) and then level at the exact same rate as if you hadn't, or you can focus on leveling now, and spend time getting plat when you're 40 and can kill hill giants (100+ plat an hour), or when you're 50 and can kill Seafuries (500+ plat an hour).
As for buying your spells, you really only need a few per level (every class has a bunch of less useful or even complete garbage spells you don't need), and ...
... you'll make enough money to buy the spells you need while you are busy earning XP.
TLDR: Don't get sidetracked by all the twinks on the server. You can earn enough plat to buy the important spells while you level, and if you focus on leveling now you'll make much more plat in the long run than if you waste time earning plat.
P.S. If you run around in crappy gear, you also increase the odds that a kind player might notice and give you some better gear.
P.P.S. If you really do want to earn plat now, another good resource is the
Treasure Hunting Guide. Admittedly the forum post Grimjaw linked has more ideas, but the wiki guide has a much more readable format.