We all know the feeders that make us end up saying stuff like "oh its free X week" so lets all help a little and give a few tips on the free champs!
1)You may want to build one of those critical Gankplanks, but please among all those phantom dancers and whatnot get some attack damage, an IE or at least a ghostblade.
2)Rageblade is a great, relatively cheap item on Kayle. A Nashors Tooth and a Malady can really help that rageblade.
3)DONT JUMP IN AS TRISTANA, unless you cleary outnumber your enemy and have full hp, I know the jump is a slow and has damage but you WILL die if you jump into 3 enemies even if you outlevel them.