Hi aj ! Welcome to the community 
You are right ! getting a controller really opens up new possibilities. I think it’s specially nice to have knobs to have hands on control 
I would advise a Beatstep pro : @Omri_Cohen has one, myself i have a first gen beatstep.
Also if you already have synths, you could use them as controllers, i often do that with my Microfreak, many synths nowadays have knobs that send midi messages.
If you need any more advice / recomendations, you can ask 
Cheers !