Crash-course for playing Chaos Space Marines
Hello! I am The nameless Commander, welcome to my quick guide on how to generally play Chaos Space Marines. This is a fairly damage-oriented army, and should be played that way. I will get straight to some key points.

Start by ordering your Heretic to construct a Plasma generator, followed by queuing 2 Cultist squads and an additional Heretic. Send your Cultists squads for capping immediately as they spawn towards the nearest Strategic points. Once the plasma generator is up, construct a Chaos temple. Have the second Heretic help out, until the first Strategic point is captured. Redirect him to constructing a Listening post at once. Once the Chaos temple is completed, have a second Listening post started ASAP. Queue the Chaos Lord and construct an Armory as soon as the second Listening post is up. Upon the completion of the Armory, queue a squad of Chaos Marines and purchase one of these upgrades from the Armory: 1) Plasma pistols, if you are fighting Necrons, Space Marines or Chaos; 2) Power Swords if you are going for Raptors. Queue a second squad of Chaos Marines or a Raptor squad. Upgrade both squads with Aspiring champions, especially if you face one of the 3 aforementioned races. You can’t go wrong with Aspiring Champions, as the Frenzy ability is useful in any seemingly even engagement, and they are carrying the power/plasma weapons which are very effective against heavy infantry, such as Tactical Marines or Necron Warriors. Should you be facing any of the other races, equip your Chaos Marines with Heavy bolters, which are very effective against light infantry. All of this should allow you to put on your opponent under pressure from the start. If needed, queue another Chaos Marine squad.

If you managed to get an early advantage, going for the Machine pit and a few extra Plasma generators is advised. An early advantage means an opponent more or less cornered in his base. The Defiler is a jack-of-all trades unit, best at bombarding enemy positions. It is the most versatile, but weakest walker. Should you NOT have obtained the early game advantage, go for the Sacrificial Circle. The Horror Squad is a relatively inexpensive dedicated anti-armor unit with a pretty good range. Make sure to upgrade your listening posts if you have extra power, it’ll prevent harassment. The Sacrificial Circle also houses numerous upgrades for your commanders. If your opponent is relying on jump-jet troops, such as Assault Space Marines or Stormboyz, purchase the Furious Charge upgrade and the Frag-grenade upgrade, which gives a notable melee damage boost to your Chaos Marines. Combined with well-timed use of grenades and the Frenzy ability will help turn the tide against jump-ins. However, fighting a squad of Sluggas/Nobs the Mekboy teleports in in melee is out of question. Frag-grenades help disrupt them and move the attacked squad out of melee, while gunning the downed enemies with the heavy bolters of the other squad(s). 3(4) Squads of Marines or 2(3) Marine and 1 Raptor Squad should be more or less doing the job, unless it's serious infantry play.

Chaos Space Marines don’t lack powerful late-game units. Depending on your opponent’s preferences (melee or ranged), purchase the Obliterator Squad or the Possessed Marines first. Rather than researching the Chaos Energies upgrade, you might want to research the Daemon Prince transformation for the Chaos Lord first. The Daemon Prince is a powerful unit with a quick regeneration rate and is strong against every type of unit. You should be wary of Gray Knights though. Keep a few squads with Chaos Marines upgraded with plasma rifles close to him. Chaos Marines with plasma rifles can gun down even Terminators with frightening efficiency. Also, make sure to purchase Infiltration for them. If nothing else, it will force the enemy to employ and manage detector units.

Well, I hope this guide will be helpful. I tried to keep it down to bare-bones and encourage you to be creative and shape your own strategies. Regard this guide as a small help, not an elaborate how-to. For the Dark Gods!