I can beat it on my own

, when you make a new version (if) make it challenging, you said in your tutorial about it getting harder as you progress, maybe at the start people could choose their own difficulty?
anyway, i reckon that all the races are well balanced and equal so whichever one you start with, it's gonna be just as easy/difficult using the others.
Some towers are fast, some are slow, some are strong and some are weak but i would usually do a normal maze starting as close to the spawn as you can, remembering not to block.
THEN you do spiral mazes around the check point area thingy

. Assuming that you get lots of money at that stage, you want to build the strongest towers possible.
Soon after loads of mini-games and creep killing, the monsters will have proven to get tougher and tougher, so you need to build varieties of towers and then build the ultimate tower (in one race in the version i played, it was an illidan model tower).
I've practiced on other TDs on roc but this one was totally different and for once i actually enjoyed it

, no horribly advanced skills are required except for the mini-games.
The mini-games test your skills against all different kinds of maps, such as racing, reaction, snipers, mazes and collecting. You will need to play lots of them.
Luckily, i always win at the maze because i spend most of my time on bnet playing mazes like maze of skill, labyrinth of nightmare, and i train on my own map labyrinth of wanders. I recommend labyrinth of nightmare, that really tests your skills.
Anyway, some mini-games you have a unit who must shoot targets and kills things. Some you must race to things to win and others, you simply have to survive

.
Make sure you get lots of practice or simply listen to Ryoko's advice and watch other people's replays

.
Have fun playing and good luck with it
~Jindo