sounds like you've got a lot going on already. the beautiful thing about painting is you don't need a plan. if you have a plan you can change plans mid-stream. i think if you start sketching you will have ideas emerge (on your own). and do more than just one sketch if you get blocked (or use...
If you're asking this question, go for acrylics. Both oil and watercolor require a bit of instruction for either preparation of the painting surface; or in the technique mixing paints and cleaning brushes, drying time, etc. If you just wanna start painting, acrylics is for you. They are...