There are 3 places you can acquire your items.
The Fountain:This is where you can get most of your items, if your inventory space is full or you are not at the fountain, the items you purchased are put in a stash. You can have the courier put items from your stash and deliver them to you.
Sideshop: These are located at the far left top lane, far right bottom lane. You can acquire SOME items from the secret shop/fountain, this means you don't risk your courier getting killed.
The (Not-so) Secret Shop: Located between mid and top for Radiant. Mid and Bottom for Dire. There are exclusive items bought here( usually for late game items) expensive and give great stats.
Items are given a price next to it in the shop menu. On how to acquire gold watch this video
 
That moment when you mistake what a person says. #firstworldproblems
(ノಠ益ಠ)ノ彡┻━┻
But if you are referring to weapons and misc. It's a random percent drop every game you play or you get a garunteed drop each level of Battlepoints. Dota economy doesn't really have set price people just trade things with the same rarity 1:1
 
The DoTA trading community is extremely small and without any real set price standards or promos like bills or buds.
 
That moment when you mistake what a person says. #firstworldproblems
(ノಠ益ಠ)ノ彡┻━┻
But if you are referring to weapons and misc. It's a random percent drop every game you play or you get a garunteed drop each level of Battlepoints. Dota economy doesn't really have set price people just trade things with the same rarity 1:1
You ninja edited me :ohno:
 
Small spreadsheets are starting to come out however but nobody really uses them, if anything some communities discourage using them.
 
So if I buy stuff from the shops, are the items tradable? And basically by now its a matter of whoever gives the best offer selling wise.
 
Play against bots while reading some guides online. Stick to a few heroes in the beginning until you know what to do.