I want to clarify this before I actually delete the site from my bookmarks:
I can't buy and sell characters until I spend real money?
Without that, there's no real changes you can make to the original 8 characters you get?
If this is true, like I said, I'll be leaving the game. I hope it's not, since it seems like a decent timewaster, and fairly fun.
to be honest, i played UR without buying credits until i reached level 48 or so. all you need is to learn how to play the game well. take it one step at a time. try to make a good deck first, then slowly work your way up in the ranks of dailies. earn clintz, buy cards, then improve your deck more!
you can join guilds! some guilds even give out credits as prizes in their own guild tournaments.
It's not as hard as you think. i started playing 18/07/07 and my first tourney win was 20/01/08. at one point, i thought of stopping but i decided to continue nonetheless...
my first "true" effective deck was T1 rescue and with that deck, i slowly moved up the ranks to buy good non-Rescue cards. i joined private tournaments even if i couldn't buy all the other good cards. at some point, i even sold Charlie, Bryan, Marina, and 2 Timbers just to buy all the cards that i needed for a private tournament...... which i lost. hahah but still, i didnt quit.
finally, when i discovered my own playstyle, i practiced and developed it even more... reaching level 48 with cards nearly as many as those in the Imperator rank. that's when i decided to buy credits with the help of a friend... if i had waited a bit longer, i could've won credits too when i entered the guild im in right now.
see, it's all about commitment and hardwork. people think money's the only thing that runs the work.. but people forget, to get money (honestly), you only need time and effort.