For good storage you can get right off the bat, join the Mage College in Winterhold. You get a free room with 8 or 9 storage containers all right close to each other - very handy for sorting your stuff (eg smithing, alchemy, enchantables, loot for selling, junk for hoarding, etc).
don't use the barrels. lost a ebony sword that way. the barrels reset every two in-game weeks, but the wardrobes never reset.
I try to keep flawless gems (you'll need some for various quests), a gold ore, a couple of mammoth tusks, jazbay graqes, fire salts, frost salts and ice wraith teeth (needed for people in Riften and a couple of other places), nirnroots (also Riften), any bow with someone's name (these won't bug the quests, it's just the musical instruments that are tricky - and you can give them to their owner once you run into them).
You're telling me I shouldn't have sold my flawless diamond?
There is also
Spoiler the Steed Stone, which gives you +100 carry weight and also removes the encumbrance of your armour ... not sure if this is a spoiler, but writing it here just in case! The Steed Stone is west of Solitude
Spoiler the knowledge isn't a spoiler, but the location is
Ok another question. In one of my next missions I think I will be going to battle Whiterun, only thing is I purchased a house there. Will I lose the house (and possessions)?
don't think so, but I did these quests before I got a house (I just use the college room (it's free)). in fact, I don't have a house yet.