I don't have a codex at hand so building you a list is going to be difficult, however I can discuss the virtues of various elements in a foot slogging army.
Autarch (w/ mandiblaster, warp pack or wings, making it magnetized for a variety of gear)
Unfortunately an Autarch is of little to no use in an army like this. His hand to hand power is minimal compared to his price and unless you are going to have some units in reserve often (outflanking scorpions or the like) the +1 to reserve rolls will also be useless.
Farseer
Probably one of the better
HQ options. You can either give him fortune and doom and mix him in with your forward units or give him guide (and maybe fortune too) and put him in with your back field units. In general though, with the options you have here, putting him in a forward position is probably the best idea.
Warlocks w/ Witchblades x4, Warlocks w/ Spears x3
Running a seer council with the farseer would work really well as a tough unit to screen your softer forward troop units. The shining spears will also help your lack of anti tank ability (although you have to get crazy close to use it. Give the squad embolden and your farseer can re-roll his psi tests. Pepper in an enhance and maybe a couple of destructors (if you don't just plan on running into hand to hand) and you'll be set. If you give out some warlocks to the guardian squads, make sure you give out the witchblade ones since the singing spears will just go to waste in back field guardian units.
Avatar
I would highly recommend using the avatar. He's tough and makes your whole army (mostly) fearless. Can't go wrong there.
Eldrad
Whiles he's great for the points, I always feel scummy if I use him or recommend that someone else does. So take that as you will.
all the Lords except Fuegan
I don't think you really have the models necessary to put the phoenix lords to good use. The only one that might fit into your army would be Jain Zar, but without a transport, he squad is going to get chewed up badly. As much as it pains me to say it, its probably best to leave the Phoenix Lords on the shelf for the time being.
striking Scorpions x5 exarch w/ claw
You simply don't have enough models to make this unit effective. I would never hit the field with less than 8 models in the squad. The lack staying power and lack punch with anything less. I too own 5 painted scorpions and they never see the field.
Fire Dragons x10 exarch w/ firepike
Another squad that's going to suffer due to lack of models. However the lack here is a transport. Without a transport, you have to bank on your opponent being stupid and moving his tanks into range of the fire dragons for them to be useful. The only time I would recommend taking fire dragons on foot is if your primary opponent plays a terminator heavy army all the time.
Banshees x10 one exarch w/ mirrorswords & one w/ executioner
Without a transport, this unit will suffer, but unlike the dragons, they are not reduced to worthlessness. What you will need to do is run them up behind a screen created by the seer council. This will ensure that they get 4+ cover saves all the time while they are moving up to get into assault. In the foot slogging case though, you MUST bring a full squad of 10, you have no choice. As for the exarch, the exarch powers for banshees are fairly useless but cheep if you have points laying around. Mirrorswords and the executioner are statistically the same so field which ever you like the most.
Harlequins x5 troupe master, seer, x3 kisses
Quins are ok, but without a shadow seer (or a transport) they are worthless. Either use the troupe master as a shadowseer or leave the squad on the shelf. If you do bring them though, they make a great screening unit for troops behind them (units behind them get 4+ cover and the enemy has to roll against the veil of tear if they want to shoot the quins).
Dire Avengers x20 exarchs w/ twin 'cats, pw/ss, and pw/ss
Dire avengers are decent foot troops. Run them up till they get close enough to shoot. Just remember that they don't do much (if anything) in hand to hand. Even with all the close combat upgrades you can give them, they only become decent at not dieing rather than doing any actual damage. You'll need to keep quins or banshees around to bail these guys out once they get into hand to hand.
Rangers/Pathfinders x5
A great unit that works well at any squad size. Always upgrade them to pathfinders as the increase in both offensive and defensive ability is well worth the points. These are the best back field objective holders you could possibly have.
Guardians x20 (I'll be getting more eventually, probably another 20)
Guardians are also decent troops if you understand their role. Their role is to be guardians and guard objectives. Basically what that means is that you take small to mid sized squads of them and move them onto back field objectives to hold them. You can also march guardians forward along with (or just slightly behind) the rest of your force. Once you steam roll over an objective, the guardians can stick around and hold the objective while the remainder of the army continues on. Putting scatter lasers or missile launchers in the squad will see that they have some decent long range fire power regardless of where they are. Also, a warlock with embolden will ensure that they don't break and run.
Warp Spiders x6 exarch has twin spinners, but I might model one to have a spinnerette rifle - anyone have any good pics of one?
I've never really found a good use for warp spiders. They are one of the fastest units you have available but their short range weaponry and the temptation to run them off into unsupported situations generally just gets them killed. You could try to use them as a stop gap unit that can zip around your lines to lend help where ever it is needed, but you have to be careful not to get them in front of your lines.
Swooping Hawks x5 exarch has sunrifle
Some of my favorite
GW models and also the worst unit in the eldar codex (probably). They are simply too expensive for the minimal ability. Las blasters just don't do enough damage for the cost and the same goes for the hawk bombs. Trying to use intercept and have them be hand to hand vehicle hunters is just a death wish for them since tanks are back row units these days and that means you got a whole army shooting at T3 4+ save guys that are expensive. All in all, the unit is a no go.
Dark Reapers x10 exarchs w/ EML, Shuriken Cannon, and the old one w/ web of skulls
Dark reapers are going to be your biggest source of troop killing. Nothing else you can field (or possibly in the whole codex other than arguably war walkers) can put out the troop killing power that reapers can. Make sure you give your exarch a tempest launcher (I use the web of skulls model for it) and crack shot. You'll then be lobbing 2 templates that scatter
2d6-5 (if they scatter at all) that re-roll to wound rolls and ignore cover. I've had my reaper exarch wipe out 8 man squads by himself (before the other reapers in the squad fired). And while cover is becoming more common, you can make sure your opponent stays in it (and thus slows his advance) by pointing a bunch of
AP 3 weapons in his direction.
Wraithlords x2 (see weapons platforms for options)
Unfortunately, this is going to really be your only source of anti tank power so make sure you put it to use. Put a missile launcher and a bright lance on these guys and send them off.
Warwalker x1 (same as WL's)
While I love war walkers, fielding less than a squad of 3 just isn't very effective. You have much better options for your heavy support slots, so don't waste one on a single war walker.
