How to play a "General"

It is all about not focusing on the minions. You don't go to steak house to just eat mash potatoes.

Don't buy creeps from citadel unless you have 12k+ gold to spend on priest+angel+catapaultsari in 1 go. Getting priest early only feed enemy DGs. (creeps = reinforcements = monsters from portal; minions = general summons)

Start with idols or not depending who you are up against. (buy -> summon -> sell idol currently is very helpful) Regulus and Torch bearer have the most trouble against minions at the start.

They do not give exp/gold to enemy.

Erebus.

No problem.

Honestly, I don't feel minions are worth it as Sedna or Oak. They are a gear option, not a requirement. I would even recommend skipping the yetis and spirit summoning skills in most cases.

The other two I always see with summoned minions, and sometimes the idols as well.   

spirit summoning increases oak's strength faster than soul power (as long as soul power is at rank 1), so I wouldn't recommend skipping this part of the build.

I think Oak with spirits is an incredibly powerful build...if you have the common sense to micro. Being able to kite an overzealous regulus or other DG while 5-10 spirits pound on him as he tries to chase you then as he gets low you get to turn on him to get the kill is reason enough.

Big thing about Oak and spirits is you arent too strong early game so you just have to focus on not dying but once you get bout 6-7 you can pretty much stay in any lane and go toe to toe with any DG often times getting the kill.

There are many different ways to play each Demigod.  I play Oak mostly, and his spirits are a BIG part of my DPS.

>"Is it all about minions and focussing on them?"
The minions are half of it, yes.  It really helps to think of the minions as a seperate force from your demigod (a much more "expendable" force).  If there is any dangerous work to be done, do not send your "very important do not die" demigod, you send the lackey squad.  For example, when an enemy Demigod appears, it is your minions which get sent to wear him down as he comes in.  And when that enemy demigod starts to flee and heads back into "dangerous territory", it is your minions that chase him down.  Get used to using the following hotkeys to select who does what:
H = select demigod
M = select all minions
N = select everything
O = minions follow demigod
Most people do not notice minion damage, because it is "a lot of little numbers", which typically gets spread among multiple targets.  But when you can focus all that scattered minion damage onto a single target, then there is no question what kind of impact minions have.  As Oak, my spirits roughly double my damage output, including the effect from the Soul Power ability.

>"Do I have to buy minions upgrade at the citadel? (i.e. +atk, +armor and +hp)"
Nope.  There are three kinds of "minions":
1) The "portal" minions, those are NOT affected by your skills/gear, and ARE affected by citadel upgrades.
2) Your "idol" minions (who follow you around), those are affected by your skills/gear (I am pretty sure), and are NOT affected by citadel upgrades.
3) Your "special" minions (who follow you around), those are affected by your skills/gear, and are NOT affected by citadel upgrades.

>"Should I start with Idols?"
I do not know what playstyle you prefer, but *I* start with Idols, every time.  Specifically, I start with a monk idol, as a 10% heal can really help in the early game, and the 22 DPS at range each puts out really helps.

>"The minions that I summon through idols, to they give xp/gold to the enemy DG?"
I never noticed.  Based on their mortality rates though, my idol minions do not die enough to give the enemy more experience than the dying enemy demigods give me.

>"Which DG has the best with minions?"
That all depends on what you consider "best" I suppose.
1) Erebus's minions do the most damage collectively, even though they look like goofy little bouncy-balls.  And are generated "for free", as long as the god is nearby when something dies.
2) Oaks minions do second best damage collectively, plus can move FAST across the map.  And are generated "real cheap", as long as the little flag is nearby when something dies.
3) Sedna and Queen minions do the most damage individually.  Queen minions do ranged/AE damage, and Sedna minions are the most durable and do AE damage at the high end.  And both can summon their minions "straight up".

I hope that helps...

its easy to play generals without focusing on their minions. as Miyamiya said, Idols are just gear options. the skill based minions have varying degrees of usefulness depending on the general. 

Queen of Thorn's Shamblers are excellent minions and I almost always use them.

Sedna's Yetis kinda suck and I rarely use them.

Erebus Nightwalkers kinda suck and I rarely focus on them, but its almost always worth getting 1 point in Coven to expand from 2 to 6 minions.

Oak's Spirits need to either be focused on or ignored. there are several powerful builds of Oak that get the entire RAise Dead BAnner skill tree line and 1 or more points in Soul Power. pretty effective build under the right circumstances. my preferred build of Oak is to just ignore the Spirit wards though and take points in Penitence, Shield, Surge of Light, and Divine Justice. 

Another point to make regarding Oak's spirits: Raise Dead Ward is real easy, cheap and fast to cast. So you can easily hit '4' and plant your flag at any time before a lane battle to keep your spirits flowing, even if they suicide or die. No need to micro them, just keep doing what you ordinarily do and work the flag planting habit into your routine and you'll get the full benefit of the Spirits.

Something else to consider. Someone posted recently (after looking at the data files) that RDW grants the Soul Power bonus even if you don't have ranks in SP. If this is true, then Soul Power has diminished value.

I read the same article, I thought that you need at least one point in Soul Power to get the bonus from the units spawned by the RDW ability, but that the 2nd and 3rd rank only increases Oak's weapon damage by 20 each.

http://forums.demigodthegame.com/350419

Yeah, you have to have 1 point in Soul Power to get the bonus.

yes, that was my research. my original interpreation was wrong. the buff does scale from 0 to 120 damage, but you need a minimum of 1 point to activate the buff. 

however, 1 point is very efficient (providing up to +80 damage for 9 spirits), whereas further points in Soul Power don't add that much at all.