BAG FOR BIKING. Whats your favorite or highly recommended? =D

Trying to find a good allround bag for almost anything =)
Found this bike on probikekit.com What do you guys think? What about saddle bags? I also heard of those backpacks that store many litres of water. Any advice would be great. Thanks =)

btw I have a Giant TCR composite 2 2006 model just incase it makes a difference in comfort.

I do not follow. Do you want a backpack to wear while you ride?

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De Rosa Planet
Campagnolo Per Sempre!
PAOLO BETTINI CAMPIONE DEL MONDO x 2!

oh just something to carry small things like lunch and shoes maybe. Yeah while I"m riding e.g. Riding to the city or a friends house I'd stop by to have some food then change into my shoes when I get to my destination