From what i have observed, most twinks play in the lvl 1-29 bracket. On a good day i am in and out of arena's constantly because there is just match after match after match...on bad days, lets just say i go do something else

. Most twinks are between lvl 25-29 in the 1-29 bracket because the better weapons/armor start at lvl 25. I usually queue for 6v6, 3v3, the mountain range, and karros canyon. and if i feel like it, i will do some 1v1, but not usually. 1v1 is usually you getting pwned, or them pwning you, there is a low chance of a fair fight in 1v1.
most twinks, to hold there own against most other twinks need about 8k HP but some have 20k+. i will say the majority of twinks have between 5k and 15k HP, while a select few have 20k+ (mosty clean statters, which really isn't fun to go up against)
it also depend on ur class, i usually play rogue in arena, and i can take out guys with double, almost triple my HP, but i can get killed in 2-3 shots
it pretty much depends whether u want to be a brick wall or a glass cannon, i chose glass cannon. most dps classes will choose glass cannon, while more defensive classes (warden, warrior, knight) will choose brick wall
another thing that i like to do is start a party for arena on my server. if i find people from my server in arena i will invite them to my party, which insures that we can all be on the same side in the team arenas/battlefields. i also do arena with friends and make a party for that also, so we are all on the same side.
and i believe in arena it is only against north american servers...but someone may want to verify that