Tides is nice due to the long cyclical periods available. Another useful modulation generator for long, generative work is the 4ms PEG which can have a great deal of variance in cycle duration/phase, plus there's a lot to be said for the various iterations of the Serge VCS (ie: Maths, Doepfer A-171-2, etc) for similar work, especially in tandem with the others. That module can also double as a user-definable-waveshape oscillator/LFO with the waveshape under CV.
As for ambient sounds, I tend to stay away from simple sine waves, since they have no harmonics that allow them to 'rise' in the mix. Instead, if I can make use of more complex waveforms and then slowly modulate their spectra via subtractive methods or, if using digital generation, by modulating the different formants themselves, this tends to give me a result that catches the ear better. It tends to mean more work in terms of programming effective sounds, but the final result is that I can have simpler compositional structures that more effectively draw a listener into the patterning, and with the gradual timbral shifting, this can be played out over rather long durations. Plus, it's worth noting that one of the most effective and beloved ambient works, Brian Eno's "1/1", has very little in the way of time-based processing aside of some basic 'room' reverberance. There's loads of different ways to approach ambient music.