Hmmm, are you going to play or just paint? If play, yeah, get a starter box! Pick the one you think look coolest, I personally like Brood the most.
If paint, you have a lot of options - what do you want to paint right now? There are tons of monsters both big (huge) and small (Brood and Skarrd), aliens (Kulkulkani and Dagyri), robots (Core), and wastelanders (Outcasts, Forsaken and Skarrd, though the latter is really freaky sado cyber mutants).
As for favourites, I like their large models a lot, like Numbskull, Abomination, Howler and the two Juggernauts. I got Numbskull and will pick up a couple of the others for my Legion points. The Archangels are also really nice models (unfortunately out of stock).
My experience is that the casts are real good with few flaws, but the metal is soft and some minis have stupid fiddly bits.