I would start thinking about effects. A nice reverb, a nice delay, maybe something like a Rain Maker or a Monsoon (expanded version of Mutable Instruments Clouds).

As far as synth modules, an Expert Sleepers Disting Mk4 is a cheap (under $200) add and has plenty of functions. An Ornaments & Crime module would serve you well as well.

Take it slow and really get to know your new stuff. Try to squeeze as much creatively out of what you have as possible... then get a feeling of where you'd like to explore. Modules like O_C and Disting are multifunctional. If you're using a particular function a lot, you might consider a dedicated module for that purpose... for example if you're using the quantizer a lot.

Don't be afraid to make a wild, one-off purchase every now and then too... sometimes something weird shakes things up a bit.