For ambient I prefer plucky bell tones or soft swelling sounds. But that's all preference. I really like Mutable Instruments Plaits for those kind of plucky patches. The percussive noise options it has can go a long way.
To get generative music you'll go a long way with something that can randomize gates or provide logic options for interesting gating. For this I use Klavis Logica XT. Another popular option is Branches by Mutable Instruments, but i think the Logica has more options for a comparable price.
You can use the MB2 LFOs on the random pulse settings to get some gate randomization, but for me it's just not there.
I will then usually use the sequencer to set up a procession of notes in a key and then set it to play random on board or through the aux channels. Since it's in the same key it's not the most generative option, but i prefer it for ambient styles because out of key notes are likely to create some tension that will break that ambiance.
