Ok here are some tips.

1-Dont be to hasty, you are not going to lose the game if you spen 20 secs cheking what to buy.

2-As you get more expirienced with the game you will be able to know what to buy before reaching the citadel or the item shop.

3-You dont need to buy things each time you got 1k,2k or 3k, i will recommend a time frame instead, each 5 or 4 minutes you go to buy new things instead, this way you will be able to get big amounts of money before buying.

4-Also you dont have to command each fight, i mean theres no reason for yo to be in each place that theres a battle, select your target, complete objective, then check your status and decide on continuing, or returning to base, and repeat.

5- And lastly calm down theres no chame in being a little slow at first, everyone is just try to pick the pace, know your demigod and know your items and you should be fine

yah, like Carlos mentioned.  the game doesnt' move as fast as it seems.

There's a lot going on, but most of it happens automatically.  Take your time, make sure you understand your items and your abilities. 

A major new player player mistake is to cast too often.

Don't overuse your abilities.  Casting at the first opportunity is a big mistake that cuases you to run out of mana when you really need it. 

If you dont' cast too much, save your mana for the right moment.  Then the game will really slow down to a maneagable pace because you're not trying to cast, guzzle mana, buy mana, guzzle health because you took too much damage because your abilities weren't ready, etc. all at the same time. 

The biggest advice: slow down... the game is not as fast as it seems.

Concentrate on keeping your demigod alive too. If you die too often and are a few levels down it can be very very hard to evade death when the enemy are a few levels higher. Had this problem last night where I died so many times as i just couldn't get away from the enemy demigods when they were like 4-5 levels higher than me.

Also, those teleport scrolls really cut down on the trips, if you've got 500g to spare. Port to base, have 20 seconds to upgrade citadel and buy stuff before the cooldown is up, port back as close as you can to where you need to be. It's worth it.

what is most important: in the beginning dont fight somewhere, where nothing happens. on big maps there are spots, where you cannot level (for example the mid in mandala, some players try to defend that healing crystal). You always need creeps at the beginning to level. so be there, where creeps are dying..^^