Boo HoL

You should probably say who you play when stating what you buy as I think that'll have an impact.

Personally I play Erebus and my first buy is always the vlemish face guard, I charge the frontlines naked and get face when I have cash for it.

After that I'll be aiming for boots of speed, then either the mana draining gauntlets or the crusader plate (depending on how long it is before I need to return to base).  

Once I've got one of those I aim for either a gold or exp upgrade at the citadel

After I've got the second one I try for minions, usually with preference to melee hero's before archers before priests, I'll try to get the highest power I can afford and then get a second idol if I've got enough left over cash

After minion purchase I'll go for either mage slayer or the cloak of flame.  My preference is usually to save up for the cloak as the gloves + the face mask is usually enough mana to keep me going and the flame AoE is GREAT for farming and also for fighting generals, not to mention the fact that it combo's really well with the erebus' life drain ability.

That's pretty late in the game though, if I've reached that level it's typically already a won game

Consummables are really dependant on the game. I generally go without any. Occasionally I will buy a health poition (matched against 2 regulus or some other equally non-sensical bullshit).

I would like to say though, the teleport scroll can be absolutely invaluable.  Everytime I am leaving the base I always check and see if I should by one to get back to the field ASAP as oposed to taking my time. Often you can teleport and get a kill/push a tower/save a tower/save a teamate/grab an important flag or any number of other useful things.

NEVER underestimate teleports. Obviously, the larger the map, the more imoprtant they are.

Right out of the gate they can be even more important ensuring your team grabs the important flag (Health Crystal, EXP) that can make a HUGE difference on that particular map.

On Topic:

In almost every game I play, I find a mageslayer in my inventory. It is the first really effective artifact you can get and generally doubles the power of your character. I really feel they need more 8k artifacts. I think 3 or 4 at 8k (not 2) that are just as effective as the mageslayer is for DPS demigods is certainly in need. Id like to see the Heart of Life get a slight buff to its passives and be moved to an 8k artifact.

Vlemish Faceguard. As was said, best Mana/gold ratio you can buy.

Gauntlets of brutality. If the character I am playing will be doing most of his damage with his base attacks it is a must have. Even then the very small investment of gold for +25 damage per hit always feels like a good investment to me.

Heart of Life, as I mentioned, its too powerful for its cost and the fact that it is now in the artifact store. In my opinion the most unbalanced item in the game. If your having trouble winning, start buying this and watch your game improve ten fold.

The last thing I almost always find ion my inventory is a way to speed myself up (boots of speed, wand of speed journeymans treads) OR something to slow my oponent down (wyrmskin gloves). If you plan on killing demigods, you need one or the other.

Not true.  If you buy it earlyish, it more than makes up for itself, the first level of it anyway.

1800/4 = 450 seconds to pay back

450/60 = 7.5 minutes

If your game lasts more than 7.5 minutes after you buy it, as a 1v1, it's worth the upgrade.

7.5 divided by the number of team mates you have will tell you how quickly the team overall will benefit from your purchase.

I should have stated that I wouldn't buy it in a 1v1 situation.  I was just saying in 1v1 it's worth the upgrade simply because of the numbers.  There are better upgrades for 1v1 that will have it beat (yours being one).  2v2 I would think differently, 3.75 minutes between the 2 of you and your partner gets a serious benefit of being able to stack his gold during that process.  Where you suffer a little for buying it, he gains as much if not more of that.  Now, he is buying artifacts instead of vendor stuff.

EDIT:  Think of it as pooling your gold, but as a process that takes 3.75 minutes instead of instant.

Usually, as a UB, I buy items in this order:

Start of game I buy:

Boots of Speed

The next three items I always buy but depending on the situation the order of purchase varies:

Guantlets of Brutality

Banded Armor

Scaled Helm

After this I buy a citadel upgrade.  Usually the gold upgrade and if that has already been purchased an xp upgrade and the tower health regen upgrade.

Then I save my money for:

Heart of Life

After I get HoL I can really start engaging towers and start pushing.

I usually spend the rest of my money on creep units and the game is usually over before I ever need to purchase an artifact.

If the game is still going at this point I will buy:

Mage Slayer

Monks, Flemish, Normoth, HoL and the occasional Citadel upgrade in between them.

I find myself buying pretty much the first tier items for most of the games....scaled helm, banded armor, scaled armor....and then cit upgrades.

I usually upgrade to a flemish faceguard as soon as possible as I tend towards skill builds and need the mana. Other than that I usually tailor my items to what I'm facing. Autoattacks? Stack armor. Skill dmg? Stack health...etc.

I've been playing a Tower Rook, recently, and focusing on defense.  my first purchase is the Scaled Helm, which usually solves most of my mana issues, and then I'll start stacking armors - Nimoth's first, for the unbeatable gold-to-defense ratio it packs, and then I like to get Armor of Vengeance to punish my attackers.  What I buy next depends on the map and oponents.  Groffling is really good against fast attack speed oponents - Regulus, UB, and Rook (whose towers aparently can trigger the 3% chance of shielding).  Saving up for artifacts can also be nice - I like the cloak of elfinkind for the huge boost to mobility, the 15% dodge, and the extra armor.  It's also pretty cheap, as artifacts go.

TP scrolls are kind of a given.  Even if you take amulet of teleport, the faster cooldown on TP scrolls still makes them occassionally useful.  Flag locks are amazing, and can easily be the difference between victory and defeat.

I'd also like to give a shout-out to the cheapest item in the game, the Totem of Revelation.  The +5 vision bonus is passive - you get it just for having one in your inventory, and it can easily open up a whole new set of strategies.  Buy one unless you're playing without Fog.

Flag locks. Lots and lots of flag locks.

As UB I play like this

First 1000 I buy a Teleport, a Hp Pot and a Mana pot x2

afterwards I buy Tower regen and usually mint (2v2 or higher, never in 1v1) then save for HoL

After HoL I usually buy whatever hp/armor chest looks good and slayer's wraps

By now the game is usually over, and ill buy mageslayer.

I get swift anklet for favor, no need to buy boots.

im open to criticism and pointers

As Sedna, this is my general buy path.

Monks,

Building HP upgrade

Vlemish,

Plenor,

High Priest Idol

Siege Dem Idol

Nimoth Chest Armor

Minotaur Idol.

then its just preists, angels, catas, giants. Really no need for Sedna to buy items past this point, You've spend ~10k on items, now just ramp up the citadel and watch the game end. If I'm losing for some reason, I may buy the Orb of Veiled Storms late on to try to bust out of my defenses and take the game to the enemy.

Favour is either Swift Anklet, or Tele Amulet on large maps.