Ashe, the epic tanker.
Ashe aways is the first target in team fights if u don't have a good tanker because of her dps and obvious because she is a paper champ, so, what if they focus you in a team fight and then... "oh wtf Ashe dun die?", with that build the probability of this happening is big, but, don't think you will be able to jump in and kill them all, you will be more like, ..., a tower!
Big health, something around 3-4k.
Flexible you can change 1-2 items to tank magic damage or physical.
With impaler you will have some attack e critical.
Is very funny see Yi trying to kill you (But you still have to run, not enough dps).
With the cooldown runes you can spam your ultimate (You will need some aim).
Yeah you can tank the tower!
Low dps, you might have 200 attack but only something around 1 attack speed.
If the other team is very balanced you will need to buy magic resist and defense.
You are not truly a tanker, if 2-3 get on you alone is over.
Take Flash and Ghost thats all you need, if things get bad for you, just flash out and run! Is just a waste if you die with the team (only run back if you are almost dead or if your team die before you get closer, remember, you need to keep some distance for a good ultimate), if you get back and heal you might be able to protect the tower yourself.
Only the four first items are essential, the other two can be exchanged for Sunfires(if you are fighting a melee only team), Thornmailfor Force of Nature(if you are fighting a magic only team), well normaly you don't have time for those 2 items but you can exchange according to what the other team has.
Tips and Hints:
If is your first time try to buy at least 1 health potas an tanker Ashe you cant do much before lv6.
If your on a solo lane save flash and ghost for bad situations, and if the enemy champ go tower dive to kill you and you think you can take few hits run a little back (try to not get out of the tower range) then flash back to the tower active ghost and run, but don't do it if the other champ is full hp, just run.
You will need patience, not everyone will be happy with your build, and some times it might be what will make you lose, because if one players start to talk bad about you the whole team will be affected, even if you play well.
Ashe tanker main function is to support your team and as Ashe is well know for being a carry people will always go for her first in team fights.
Pratice your shot (Ultimate) thats your money maker after farmming creeps and if your team don't have a ganker, your ultimate will have to do the job.