[hijynx]

You can't go wrong with pink horrors, plaguebearers, bloodcrushers, flamers, and fiends. Start there.

Actually, wait for plastic ones, then start.

 

[hijynx]

And remember every unit in the codex is highly specialized. You should balance out the tzeentch/slaanesh with khorne/nurgle. I usually don't use any of the slaanesh units except in low point value games, Khorne kills better, and Nurgle dies harder.