Re: How to choose what items to get? [dota2]
I take it that you know roughly most of the items in the game. I don't know how DotA 2 item interface is like. Basically the items are already grouped.
Contains mainly damage item. Look to get these if you are DPS hero.
Mainly tems with Orb effects (except Sange and Yasha). Mainly choose 1 from here. Yasha almost never fails with an Agi DPS hero. Items here are mainly gotten on DPS heroes.
Generally contains items for caster. If you are playing Casters, items here are usually useful.
Contains items that boost your Armour or HP. If you need more HP, get items from here.
Rest of the 'shops' are mainly miscellaneous stuff. The 5 I listed are generally rather pricey. In a realistic game, you are not going to be able to get them easily without having small items first. I'll give you a general rule of thumb.
1. Starting items
You start with 603 gold. Buy several small items that increases your stats. Items like Circlet Gauntlet Slippers Mantle Ironwood Branch are pretty useful. Also ensure you have Regen items like Healing Salve or Tangos. If you are melee, Stout shield is pretty useful. Having access to a courier is quite important. I usually buy my own courier in pubs.
2. Early game items
Soon you will need to farm Boots. Also, having Bracers (Str) Wraiths (Agi) or Null (Int) is pretty useful. Other useful items are Basilus (gives Mana regen and some Armour) and Poor Man Shield (usually for Agi melee heroes). Getting a Ring of Health is pretty helpful too (can upgrade it later). Cloak if you are against alot of casters. Magic Wand is useful on pretty much every hero. Bottle is sort of necessary if you are Solo Mid.
In general, if your hero is a Caster, choose Arcane Boots. If it is DPS hero, choose Power Treads or Phase Boots (probably Treads since you are new). Very late game, most would sell for Boots of Travel. If you are Tinker, always get Boots of Travel.
4. Mid game
Basically you need some survival items in the form of cheap HP. Urn/Jango/Vanguard is very helpful. Hood is good if opponent contain many casters. Vladimir is decent if you are melee hero.
Usually this applies to DPS heroes only. Generally you can only have 1 Orb per hero. They sort of overwrite each other, so you can't have multiple. HotD is the most popular because it gives Life Steal + Armour. Other Orbs is up to preferences or heroes. Note that if the hero has Orb skills in his skill set (Anti Mage, Viper etc), you generally would not want to buy any Orb items.
6. Late game
You want to stop buying small cheap items, and going for the big ones. If you are DPS hero, generally you get damage items and a choice of Orb. On Agility DPS heroes, aim to get Manta Butterfly etc at some point.
If you are a Caster, get caster items like Sheepstick, Force Staff, Cyclone or Scepter (only if hero can benefit from Scepter upgrade).
For both DPS and Casters, you might require additional survivalbility via increase in HP or Armour. Assault is pretty common for DPS, whereas Shivas is for Caster. Black King Bar if you need magic immunity. Heart is also pretty useful on any hero.
This is just a rough idea. If you have a specific hero, I can give you a general build.
PS. How did you get the key? Been trying to get one ;\