I can see potential...
To begin with what you did right, the designs of your characters fit well with the world it appears you intended to create. The concepts of the cards (what I saw of them) were interesting, and the idea surrounding the game itself is basic, but solid. As mentioned in an earlier review, the experience points system is comprehensive; if you're defeated in a fight, you just learned how not to fight, and that is reflected through earning some XP even when you don't win. However, there are a great deal of things you could do to improve this flash title.
One noticeable thing is to add more of a music variety. It may not seem all that important, but there's nothing like stepping into uncanny valley by hearing the same "Peaceful Town Music" when you begin attacking a baddie. No music would be better than one song for the whole of the game's content.
Another thing to work on would be a designated space for the menu. As it stands, the menu appears unprofessional, seemingly all over the top of the screen. One idea would be to have three options (Attack, Magic, and Battle Card) and then provide a drop-down menu to the Battle Cards section. You could even add drop downs to the others if you wanted variety in attacks and magic. Placing these options in front of a solid background would really improve the aesthetics, as well.
Something to consider would be character customization. Even something as simple as the basic Male/Female, Warrior/Mage/Thief options would give an added sense of immersion to the game.
Now, I'm sure you heard this much too often in school, but I'm gonna repeat it anyway. -Always- go back and check your work! Go over your grammar and such within dialogue and descriptions. It makes the game feel more fluid for the player when they don't have to go back and re-read because something was misspelled/missing/mixed up.
It may be more intuitive to have a separate currency for the cards and level increase. For someone just starting out, having to choose between leveling their character and getting a card that may or may not help in the long run is a really daunting decision, especially if they don't know quite what to expect from the game's opponents. This sets up a number of points:
Gold. You can't go wrong with gold, especially with the kind of atmosphere you've set up with the backgrounds and character designs. It can be anything though, if you're going for goofy (Kingdom of Loathing's "meat" currency is one example) or mystical/magical (perhaps runes?) as an alternate currency for the talismans of ancient magical creatures.
Another point previously stated by another user would be to create a tutorial. When executed correctly, this gives you a chance to set up your mythos and gives the player the little shove they need to understand what's to be expected of the world you've created. Something that may seem incredibly obvious to you might be overwhelming to a player, so go ahead and put as much detail into the tutorial as there is content to the game.
Also mentioned before: why not give new players a card, or allow them to choose one from a predetermined group? It would level the field a little, and allow the player to get acquainted with the Battle Card system early on. You could even incorporate it as part of the tutorial.
Just a nit pick: you don't need to have huge dots to define the options on the map or topics. A small, simple symbol would do. You could even correlate the icon to what the place is (forest = tree, town = little hut, etc.).
On a smaller note, assuming what a previous reviewer said is true, and these characters came from RPG Maker, it may be wise to create new character models. If you're not the best at drawing or designing, try collaborating with someone on Newgrounds who is. It wouldn't hurt to add a little more variety while you're at it, since there only seem to be so a few different designs that get repeated frequently.
Overall, it's not a bad start, so please consider what I and other reviewers have said, I'd like to see how far you can take it. :)