how wins/lost works, how battles usually play out, and what are the tiers of characters?
Win/Loss is self-explanatory. Fights themselves are left to the combatants to work out the parameters unless it is a tournament, in which case the rules are preset and must be abided by. When engaging in a fight, most of us use the T1 Eden era or some variant of those rules to conduct our fights. See my signature of you want to learn more about T1.
Ranked matches require a judge to make sure that everyone is playing fair and to settle any disputes regarding actions/defense/damage by the characters in the fight. Judges rulings are final, although a second Judge may be called upon when things get really nit-picky so establishing the judges right away prior to the fight is important when you want to ensure quick resolutions that are fair.
Tiers for characters, such as they are, are fairly simple. Human, Enhanced, Moderately Powered, then Powered. Some use Godly as well but really? No one likes fighting at those levels much. Human and Enhanced are fairly simple to discern when comparing characters. Moderately powered and Powered are where most people get snagged up. So sharing CS's with your opponent and negotiating power levels is pretty much standard.
Most of us have scalable characters which can slot into the enhanced, M-P and Powered ratings easily enough depending on whom we are facing. Others have specific characters set for each power rating.
When building a character, if there is a question, you can always submit it in the GuildHQ thread and ask for advice on how to better make the character fit into the arena framework for characters, although there is no established CS, there are important elements that have to be addressed. Powers (explained in detail), equipment (explained in enough detail to make clear what it can and cannot do.) Some backstory if you are looking to make a persistent multiverse character that can be in multiple storylines and places. Make the backstory accessible to others who may want to build upon something so there is a natural rivalry or alliance.
Have Fun.