1) Get better gear. This includes knowing which stats on gear are generally good for you and your spec.
2) Enchant your gear. Typically this can add a few percentage points to your output.
3) Some improvement can be made by reforging specific stats on your equipment to ones that are more beneficial to your class and spec.
4) Know your class and spec. Each combination will have specific spell priority lists (used to be rotations, but that has gone out of favour) that will maximize your output.
5) At maximum level sites like the Elitist Jerks forum (don't let the name put you off) can supply a lot of information about maximizing your character. Whlst some of this information is irrelevant to people levelling because they don't yet have access to the full range of spells and abilities, they can at least start recognising which spells to emphasize in their play to give the best results.
6) Do what you have done here. Ask the community for advice. Also try reading the eu.battle.net class forums.
All this advice is generic I know, but hopefully you will be able to pick enough out of it to help you.
I haven't played fire (yet) so I'm not an expert on your rotation (which, as Sylkh points out, is now more correctly called a priority list).
I suspect that enchanting and reforging are probably best left until you're higher than level 38.
Better gear certainly helps massively, but yours isn't bad. I see a lot of Spirit on your gear. I'm not sure whether you went looking for it, or it's just the random drops that were available. Spirit doesn't help you much as a mage, though I remember when starting I thought that it should, before I started crunching numbers. At your level, you just want Intellect and Stamina, in that order, with Crit and Hit as nice bonuses if you happen to get them.
Mostly, I suspect you just need to practice your rotation. I'm going to provide a link to a post I made earlier with the best advice I have on the subject:
If it's any comfort, I'm struggling with dps on a Ret Paladin alt at the moment. I know about all the theory stuff, and I know what I should be doing, but I'm not pre-hitting the keys fast enough, not catching procs fast enough when they happen, and missing out on some of my lesser-used attacks. I know all this. I just have to practice, practice, practice. My rep is now Hated with Target Dummies. :)