The reason the 450 champs are the 450 champs are because Riot thought they're good 'basic' all-around champs, and lower skill mastery (not saying they're all EZ MODE no skill champs, but picking up the basics of them/playing them at 'ok' levels takes very little compared to say...
) So you wouldn't be hurting too bad needing a champ of any role besides the free week ones.
I think they did a pretty good job picking the right ones. :)
good tank, easy q/r/e combo, pretty much all builds that involve a lot of max hp are viable on him.
easy burst mage, not extremely squishy (cause of E and tibbers being sort of a pseudo-tank.)
easy adc, good AA's, probably one of the best last hitters in the game, W- easiest skill in the game to learn IMO.
SUPER easy combo fighter, you pretty much cannot fuck up his combo, just QWE in pretty much any order and run at them, you're bound to do something (maybe not the best thing you could do, but just learning when to faceroll and go in can get you decent at the bruiser roll.)
just spam heals on your adc and you won't completely fail as a support. (as opposed to
or something where you'll just drain your mana, miss all your bubbles, and heal for very little, if played at a low skill level)
/
literally does not matter what runes and masteries you use, you'll still come out of the jungle at full health, maybe sub-optimal clear speed, but at least you're not gonna die to your own blue buff.
Annd..yah got yourself a full team comp with even a few subs
Also Sivir atm is considered one of the 'best' champs, if you go by pro-play.
Yay for rito not being 'pay to win'
xD