DotA Items cost and recipes

Items cost and recipes
Try to remember the hot keys for the items and the shop which sell them. this will reduce the time you are in the fountain and let you be on your way to help or gank heroes faster. As 30 seconds per visit to the shops will be 10 mins if you had visited 20 times. The recommended time spent on buying should be around 2 seconds per visit using the hot keys to help. This way even 30 visits will only be a 1 minute spent in the whole duration of the game.

It's a good thing to remember all the item cost and the recipes of some of the more common used items such as Power Treads, Butterfly, Batterfury etcs. As once you are sure of the cost you will be able to go for some of the cheaper items for your build 1st. This will help you to increase your hero's stats and damage slowly with each items, than compared to going for a sacred relic which cost 3800 gold.

However, if you are good enough in last hitting to farm and play the game with a limited items early; you can go for the sacred relic or other higher level items such as a level 4 butterfly. As once you get the level 4 items during the early game you are near unstoppable and can easily end the game there, if your team is doing well as well. This is only recommended if you are already very good in the game and can do without any items for the period where you farm up for the relic. As the longer you hold on to your gold until 3800, the longer is the time your hero is low on damage and survivability. you will likely be a target for the more "items developed" heroes.

When choosing the items to buy
You have to think about how your hero is going to be used as. If he should be a tank go for HP, HP regeneration and Strength items with high armour. While a DPS hero should go for damage, attack speed or agility items. Nuker/Diabler heroes should go for more items to diable or more hp/mana/survivability to increase the duration of the fight to be able to cast their nukes again.

Another thing to note is to take into consideration the skills set of that particular hero, and think of ways to either utilise them or increase their effectiveness.

So all together, if your items meet the hero's class (Tanker/DPS/Nuker etcs) and the hero's skill set. Your hero will be well balanced and be able to do very well in the game.