There are a lot of guides for all kinds of situation but this a special guide. I recommend reading it after you lost a match, maybe it will cheer you up a little. New players might find one or two useful tips. I hope you enjoy it!
1. Learn the basics!
Read the manual, guides, try different builds and find out which abilities are useful for your demigod.
Check out the: Compilation of Demigod Guides by Sean0883!
You will find several very good tutorials and guides to various so called 'builds'. This will save you a lot of time to figure out what abilities to pick and which items to buy.
I can really recommend the DemigodDB (thanks a lot UhelligGudn)!
2. Game Mechanics
Try to understand how the mechanics of Demigod work. Which abilities stack (stun + UB's Foul Grasp), how war rank works, how much damage minions do, criticals, cooldowns...
Try to work toghether as a team and be nice to your fellow players!
Sometimes even unusual combinations can work out if you try hard enough.
Don't shout at at the other players or lecture them, the chat is there to help you coordinat attacks. Nobody wants to get his ear chewed off! A friendly word of advice for new players might be welcome though.
Don't be offended if your teammate seems to bark commands at you. He doesn't want to waste time and 'go right' usually means: 'Dear Sir, I wan't to go to the left lane, please be so kind and cap the flag on the right side, there will be cookies after the game.'
4. Spending Money
Money is crucial. (What a unique and little known concept...) It gets you the items and citadell upgrades you need. Even more important than to earn money is to deny your opponent money! Don't die when you can help it! The gold upgrade in the citadell is the first thing you should buy at war rank 3 - if your team can afford it. (If you are falling behind you might want to go for an item that buffs your stats or your towers first though.)
And for the Alllfathers sake don't buy the death penality reduction upgrade in the citadel! If your team dies a lot you wan't something that makes them stronger and not something that sends them back faster to get killed again!
Some items are more useful than others. Read up on the stats and don't buy something you might regret later. There are a lot of shiny objects that will only eat up your hard earned money.
Do you really need the Heart of Life or an artifact? Would it make more sense to get a citadel upgrade (Catapults, Giants!) instead and a few health potions and one or two flag locks?
5. Your Starter Kit and the first minutes
You start with just enough gold to buy the most essential items and once you have picked your favor item you are stuck with it. If you play a general get the Monk Idol for 900 gold! Nothing is more valuable than to bring you own medic to the fight!
You can cast your minions and resell the Idol for 80% (right-click on it in the shop). This will give you enough money back to get another useful item like the Banded Armor (550 gold). Some might say it is a cheap trick but for now it is a valid game mechanic. This unintended behavior of idols was removed in patch 1.10. The Monk Idol is still a very good choice for most Generals.
You might want to check out the 550 gold mana helm (Scaled Helm) if you play a mana heavy demigod (Torchy). The +4 mana boost is nothing to write home about but the helm gives you a higher base mana capacity (+525) and you might be able to squeeze out another spell or two before you have to return to the crystal.
A worrior needs armor! A good choice is the Banded Armor, it increases your health (+400) and gives you a small (+5) health regen at the same time. With 550 gold you have still enough for a teleport scroll, potions or the Gauntlets of Brutality!
There you go, fits perfectly!
If you are outnumbered or you think you won't win this fight, run!
It's better to turn your tail and run than to deliver First Blood to the other team! Should you die despite all your efforts don't quit! If you are clever and a little patient you can get back into the game without problems. Besides, if you only stick around when you are winning anyway you'll never get better! Cap a flag and farm some XP if you think you are outmatched and try to get back into the game.
Don't forget to go back and visit the crystal in time! If you have slain your opponent and are low on mana get a refill. When he comes back he will have full health and mana, are you strong enough to repel him again in a weakened condition?
Early Citadel Upgrades:
While you visit the health crystal make a little detour and buy a citadel upgrade. Your towers could use a little buff to withstand the onslaught of creeps. The two upgrades at the top will provide your towers with some health regen and additional hit points or more damage. Both level I upgrades are well worth their money and you should buy them early on.
Now the early creeps have no chance to make even a dent in your fortifications!
Woudn't it be nice to rise through the ranks faster, or to have a level advantage over your opponent? How about getting that level 5 ability you wan't so badly a little earlier? Invest 1200 gold in your citadel and buy the +10% experience upgrade! You will be one step ahead of your opponent and the more players are on your team the more it will pay off.
The other team will be in awe how fast you gain your levels and you can dominate them! Buy it as soon as possible, it won't help you if you wait until you are level 19...
You have slain the enemy and plundered their dead bodies and fortifications for money. Now it is time to spend more of your hard earned money!
Maybe you have enough money to buy some more expensive gear. A good choice might be to grab one of the more powerful mana helmets, the Vlemish Faceguard. It costs you 1750 gold but it is worth every penny!
The Plenor Battlecrown for 1500 gold has a higher additional mana volume but the +70% regeneration usually only pays off after you have increased your base mana regen to a higher value with another item.
Once you you can buy both mana will be no longer a problem for a while!
If you play a close combat demigod you want something to protect you from all the blows you recieve. Meeting new people on the field of honor takes it's toll! You might have picked up the Banded Armor already but if you are lookin for something special, take a look at the shoe tab!
The Unbreakable Boots are just what you were looking for! They will not only give you an additional 600 health and +5 regen but also +800 base mana. Thats enough for two healing spells (Sedna) or a Circle of Fire and a fireball! Careful though, don't inhale too deeply!
Citadel Upgrades, Scene II
You have secured some cash and you are on your way to buy some new equipment and hug the crystal. Hold it right there! Do you really, really need that armor you were planing to buy right away? There is one citadel upgrade, the mother of all upgrades so to speak and you have to buy it! It will help you to win in a 2v2 and in a 5v5 it will literally pay for itself in under two minutes. What am I talking about? The Currency Upgrade I (yup, the gold bars).
Let's do the math: The upgrade adds +4 gold per second. Not impressed yet? It does it for every player on your team for the rest of the game, that's 240 gold per player per minute. That is one free Narmoth's Ring for everybody on your team after 17 minutes. Or in a 3v3 enough gold to buy Catapults and Giants after 15 minutes! And I'm not even taking into consideration that you might get a few kills more because your team will have better equipment during the whole game. Buy this as soon as you can afford it, I often sell some cheap item if I don't have the 1800 gold on me.
The best way to go is if the most successful player on your team buys it at soon as it becomes available. If he is tied up somewhere or failed to buy the upgrade buy it yourself. There is one exception to the rule: If you think you can't stand up to your opponent and you need one crucial item to turn the tide. In that case get the item, farm some additional gold and come back to buy it as soon as possible.
There are many ways to work in a team. The more obvious ones include ganking an opponent with two demigods, healing an ally, investing in the citadel. Why stop there? You can drop items on the map by right-clicking on them in your character interface (hotkey'C'). Your ally can pick them up and either resell them for 80% or use them himself. Your ally is feeding the Unclean Beast? Drop a small health potion and type: 'For you!' Maybe he get's the message...
Or it's a great way to say thank you to the Sedna or Queen of Thorns player who saved your sorry butt once again. Drop a mana potion and say: 'TY!' Sedna/QoT can't have too much mana after all. Or you can coordinate buying creep upgrades. The amount of money required to go from Archers to Giants is immense but it's a very nasty surprise for the other team. Don't forget to buy flag locks too! It's amazing what you can do if you work together.
(TY for the pic Sean0883!)
Useful item combinations
You have heared of so called 'builds'. Here are some items worth their money you might want to buy if you need to boost a stat.
(TY for the pic Sean0883!)