For a low points cost, the chaos commander get a level 1 psyker. Pump him up a few mastery levels and we can get a true menace starting at 110 points for a level 3 sorcerer. Add in a mark of Tzeentch and we also unlock Thousand Sons marines as troops (if running such an army). I'll refer the interested reader back to the Chaos Lord review for the notes about getting in to close combat and rolling on the chaos boon table.
Let's have a look at a few potential builds that might be entertaining.
Sorcerer @ Level 3, Mark of Slaanesh, Steed of Slaanesh, Combi-Melta (155 points)
Ride up on the steed (along with your favourite fast moving squad to taste) and hammer with psychics. I'd suggest two rolls on telepathy as well: hope for invisibility, but take primaris if needed. The combi-melta is there for flexibility and threat to vehicles.
Speaking of telepathy, there's little wrong with just sitting your level 3 sorcerer on a bike and rolling three times on the telepathy table -- just a thought! Or even a simple level 3 sorcerer in terminator armour that is deep-striking lone-wolf style could be appealing too.
Sorcerer @ Level 3, Mark of Tzeentch, Terminator Armour, Combi-Flamer (157 points)
Place in a respectable block of Tzeentch terminators, and take your powers from Tzeentch preferentially. The combi-flamer is there for when the squad is assaulted, or opportune moments.
Sorcerer @ Level 2, Mark of Tzeentch, Disc of Tzeentch, Scrolls of Magnus, Sigil of Corruption (200 points)
A riskier proposition: take one Tzeentch power and one Telepathy. Zoom around on your disk and gain extra powers every turn. Use primarily as a fire base and try not to die hideously to enemy flyers.
Sorcerer @ Level 3, Mark of Nurgle, Palanquin of Nurgle, Sigil of Corruption (190 points)
A slow, expensive sorcerer of Nurgle with extra wounds thanks to the palanquin. Take with plague marines and go forth!